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25
26 <!DOCTYPE refentry PUBLIC @docdtd@ [
27
28 <!ENTITY seealso SYSTEM "@builddir@/see_also.sgml">
29 ]>
30
31 <refentry>
32
33 <docinfo><date>@LXC_GENERATE_DATE@</date></docinfo>
34
35 <refmeta>
36 <refentrytitle>lxc.container.conf</refentrytitle>
37 <manvolnum>5</manvolnum>
38 </refmeta>
39
40 <refnamediv>
41 <refname>lxc.container.conf</refname>
42
43 <refpurpose>
44 LXC container configuration file
45 </refpurpose>
46 </refnamediv>
47
48 <refsect1>
49 <title>Description</title>
50
51 <para>
52 LXC is the well-known and heavily tested low-level Linux container
53 runtime. It is in active development since 2008 and has proven itself in
54 critical production environments world-wide. Some of its core contributors
55 are the same people that helped to implement various well-known
56 containerization features inside the Linux kernel.
57 </para>
58
59 <para>
60 LXC's main focus is system containers. That is, containers which offer an
61 environment as close as possible as the one you'd get from a VM but
62 without the overhead that comes with running a separate kernel and
63 simulating all the hardware.
64 </para>
65
66 <para>
67 This is achieved through a combination of kernel security features such as
68 namespaces, mandatory access control and control groups.
69 </para>
70
71 <para>
72 LXC has supports unprivileged containers. Unprivileged containers are
73 containers that are run without any privilege. This requires support for
74 user namespaces in the kernel that the container is run on. LXC was the
75 first runtime to support unprivileged containers after user namespaces
76 were merged into the mainline kernel.
77 </para>
78
79 <para>
80 In essence, user namespaces isolate given sets of UIDs and GIDs. This is
81 achieved by establishing a mapping between a range of UIDs and GIDs on the
82 host to a different (unprivileged) range of UIDs and GIDs in the
83 container. The kernel will translate this mapping in such a way that
84 inside the container all UIDs and GIDs appear as you would expect from the
85 host whereas on the host these UIDs and GIDs are in fact unprivileged. For
86 example, a process running as UID and GID 0 inside the container might
87 appear as UID and GID 100000 on the host. The implementation and working
88 details can be gathered from the corresponding user namespace man page.
89 UID and GID mappings can be defined with the <option>lxc.idmap</option>
90 key.
91 </para>
92
93 <para>
94 Linux containers are defined with a simple configuration file. Each
95 option in the configuration file has the form <command>key =
96 value</command> fitting in one line. The "#" character means the line is a
97 comment. List options, like capabilities and cgroups options, can be used
98 with no value to clear any previously defined values of that option.
99 </para>
100
101 <para>
102 LXC namespaces configuration keys by using single dots. This means complex
103 configuration keys such as <option>lxc.net.0</option> expose various
104 subkeys such as <option>lxc.net.0.type</option>,
105 <option>lxc.net.0.link</option>, <option>lxc.net.0.ipv6.address</option>, and
106 others for even more fine-grained configuration.
107 </para>
108
109 <refsect2>
110 <title>Configuration</title>
111 <para>
112 In order to ease administration of multiple related containers, it is
113 possible to have a container configuration file cause another file to be
114 loaded. For instance, network configuration can be defined in one common
115 file which is included by multiple containers. Then, if the containers
116 are moved to another host, only one file may need to be updated.
117 </para>
118
119 <variablelist>
120 <varlistentry>
121 <term>
122 <option>lxc.include</option>
123 </term>
124 <listitem>
125 <para>
126 Specify the file to be included. The included file must be
127 in the same valid lxc configuration file format.
128 </para>
129 </listitem>
130 </varlistentry>
131 </variablelist>
132 </refsect2>
133
134 <refsect2>
135 <title>Architecture</title>
136 <para>
137 Allows one to set the architecture for the container. For example, set a
138 32bits architecture for a container running 32bits binaries on a 64bits
139 host. This fixes the container scripts which rely on the architecture to
140 do some work like downloading the packages.
141 </para>
142
143 <variablelist>
144 <varlistentry>
145 <term>
146 <option>lxc.arch</option>
147 </term>
148 <listitem>
149 <para>
150 Specify the architecture for the container.
151 </para>
152 <para>
153 Some valid options are
154 <option>x86</option>,
155 <option>i686</option>,
156 <option>x86_64</option>,
157 <option>amd64</option>
158 </para>
159 </listitem>
160 </varlistentry>
161 </variablelist>
162
163 </refsect2>
164
165 <refsect2>
166 <title>Hostname</title>
167 <para>
168 The utsname section defines the hostname to be set for the container.
169 That means the container can set its own hostname without changing the
170 one from the system. That makes the hostname private for the container.
171 </para>
172 <variablelist>
173 <varlistentry>
174 <term>
175 <option>lxc.uts.name</option>
176 </term>
177 <listitem>
178 <para>
179 specify the hostname for the container
180 </para>
181 </listitem>
182 </varlistentry>
183 </variablelist>
184 </refsect2>
185
186 <refsect2>
187 <title>Halt signal</title>
188 <para>
189 Allows one to specify signal name or number sent to the container's
190 init process to cleanly shutdown the container. Different init systems
191 could use different signals to perform clean shutdown sequence. This
192 option allows the signal to be specified in kill(1) fashion, e.g.
193 SIGPWR, SIGRTMIN+14, SIGRTMAX-10 or plain number. The default signal is
194 SIGPWR.
195 </para>
196 <variablelist>
197 <varlistentry>
198 <term>
199 <option>lxc.signal.halt</option>
200 </term>
201 <listitem>
202 <para>
203 specify the signal used to halt the container
204 </para>
205 </listitem>
206 </varlistentry>
207 </variablelist>
208 </refsect2>
209
210 <refsect2>
211 <title>Reboot signal</title>
212 <para>
213 Allows one to specify signal name or number to reboot the container.
214 This option allows signal to be specified in kill(1) fashion, e.g.
215 SIGTERM, SIGRTMIN+14, SIGRTMAX-10 or plain number. The default signal
216 is SIGINT.
217 </para>
218 <variablelist>
219 <varlistentry>
220 <term>
221 <option>lxc.signal.reboot</option>
222 </term>
223 <listitem>
224 <para>
225 specify the signal used to reboot the container
226 </para>
227 </listitem>
228 </varlistentry>
229 </variablelist>
230 </refsect2>
231
232 <refsect2>
233 <title>Stop signal</title>
234 <para>
235 Allows one to specify signal name or number to forcibly shutdown the
236 container. This option allows signal to be specified in kill(1) fashion,
237 e.g. SIGKILL, SIGRTMIN+14, SIGRTMAX-10 or plain number. The default
238 signal is SIGKILL.
239 </para>
240 <variablelist>
241 <varlistentry>
242 <term>
243 <option>lxc.signal.stop</option>
244 </term>
245 <listitem>
246 <para>
247 specify the signal used to stop the container
248 </para>
249 </listitem>
250 </varlistentry>
251 </variablelist>
252 </refsect2>
253
254 <refsect2>
255 <title>Init command</title>
256 <para>
257 Sets the command to use as the init system for the containers.
258 </para>
259 <variablelist>
260 <varlistentry>
261 <term>
262 <option>lxc.execute.cmd</option>
263 </term>
264 <listitem>
265 <para>
266 Absolute path from container rootfs to the binary to run by default. This
267 mostly makes sense for <command>lxc-execute</command>.
268 </para>
269 </listitem>
270 </varlistentry>
271 </variablelist>
272 <variablelist>
273 <varlistentry>
274 <term>
275 <option>lxc.init.cmd</option>
276 </term>
277 <listitem>
278 <para>
279 Absolute path from container rootfs to the binary to use as init. This
280 mostly makes sense for <command>lxc-start</command>. Default is <command>/sbin/init</command>.
281 </para>
282 </listitem>
283 </varlistentry>
284 </variablelist>
285 </refsect2>
286
287 <refsect2>
288 <title>Init working directory</title>
289 <para>
290 Sets the absolute path inside the container as the working directory for the containers.
291 LXC will switch to this directory before executing init.
292 </para>
293 <variablelist>
294 <varlistentry>
295 <term>
296 <option>lxc.init.cwd</option>
297 </term>
298 <listitem>
299 <para>
300 Absolute path inside the container to use as the working directory.
301 </para>
302 </listitem>
303 </varlistentry>
304 </variablelist>
305 </refsect2>
306
307 <refsect2>
308 <title>Init ID</title>
309 <para>
310 Sets the UID/GID to use for the init system, and subsequent commands.
311 Note that using a non-root UID when booting a system container will
312 likely not work due to missing privileges. Setting the UID/GID is mostly
313 useful when running application containers.
314
315 Defaults to: UID(0), GID(0)
316 </para>
317 <variablelist>
318 <varlistentry>
319 <term>
320 <option>lxc.init.uid</option>
321 </term>
322 <listitem>
323 <para>
324 UID to use for init.
325 </para>
326 </listitem>
327 </varlistentry>
328 <varlistentry>
329 <term>
330 <option>lxc.init.gid</option>
331 </term>
332 <listitem>
333 <para>
334 GID to use for init.
335 </para>
336 </listitem>
337 </varlistentry>
338 </variablelist>
339 </refsect2>
340
341 <refsect2>
342 <title>Proc</title>
343 <para>
344 Configure proc filesystem for the container.
345 </para>
346 <variablelist>
347 <varlistentry>
348 <term>
349 <option>lxc.proc.[proc file name]</option>
350 </term>
351 <listitem>
352 <para>
353 Specify the proc file name to be set. The file name available
354 are those listed under /proc/PID/.
355 Example:
356 </para>
357 <programlisting>
358 lxc.proc.oom_score_adj = 10
359 </programlisting>
360 </listitem>
361 </varlistentry>
362 </variablelist>
363 </refsect2>
364
365 <refsect2>
366 <title>Ephemeral</title>
367 <para>
368 Allows one to specify whether a container will be destroyed on shutdown.
369 </para>
370 <variablelist>
371 <varlistentry>
372 <term>
373 <option>lxc.ephemeral</option>
374 </term>
375 <listitem>
376 <para>
377 The only allowed values are 0 and 1. Set this to 1 to destroy a
378 container on shutdown.
379 </para>
380 </listitem>
381 </varlistentry>
382 </variablelist>
383 </refsect2>
384
385 <refsect2>
386 <title>Network</title>
387 <para>
388 The network section defines how the network is virtualized in
389 the container. The network virtualization acts at layer
390 two. In order to use the network virtualization, parameters
391 must be specified to define the network interfaces of the
392 container. Several virtual interfaces can be assigned and used
393 in a container even if the system has only one physical
394 network interface.
395 </para>
396 <variablelist>
397 <varlistentry>
398 <term>
399 <option>lxc.net</option>
400 </term>
401 <listitem>
402 <para>
403 may be used without a value to clear all previous network options.
404 </para>
405 </listitem>
406 </varlistentry>
407 <varlistentry>
408 <term>
409 <option>lxc.net.[i].type</option>
410 </term>
411 <listitem>
412 <para>
413 specify what kind of network virtualization to be used
414 for the container.
415 Multiple networks can be specified by using an additional index
416 <option>i</option>
417 after all <option>lxc.net.*</option> keys. For example,
418 <option>lxc.net.0.type = veth</option> and
419 <option>lxc.net.1.type = veth</option> specify two different
420 networks of the same type. All keys sharing the same index
421 <option>i</option> will be treated as belonging to the same
422 network. For example, <option>lxc.net.0.link = br0</option>
423 will belong to <option>lxc.net.0.type</option>.
424 Currently, the different virtualization types can be:
425 </para>
426
427 <para>
428 <option>none:</option> will cause the container to share
429 the host's network namespace. This means the host
430 network devices are usable in the container. It also
431 means that if both the container and host have upstart as
432 init, 'halt' in a container (for instance) will shut down the
433 host.
434 </para>
435
436 <para>
437 <option>empty:</option> will create only the loopback
438 interface.
439 </para>
440
441 <para>
442 <option>veth:</option> a virtual ethernet pair
443 device is created with one side assigned to the container
444 and the other side attached to a bridge specified by
445 the <option>lxc.net.[i].link</option> option.
446 If the bridge is not specified, then the veth pair device
447 will be created but not attached to any bridge.
448 Otherwise, the bridge has to be created on the system
449 before starting the container.
450 <command>lxc</command> won't handle any
451 configuration outside of the container.
452 By default, <command>lxc</command> chooses a name for the
453 network device belonging to the outside of the
454 container, but if you wish to handle
455 this name yourselves, you can tell <command>lxc</command>
456 to set a specific name with
457 the <option>lxc.net.[i].veth.pair</option> option (except for
458 unprivileged containers where this option is ignored for security
459 reasons).
460 </para>
461
462 <para>
463 <option>vlan:</option> a vlan interface is linked with
464 the interface specified by
465 the <option>lxc.net.[i].link</option> and assigned to
466 the container. The vlan identifier is specified with the
467 option <option>lxc.net.[i].vlan.id</option>.
468 </para>
469
470 <para>
471 <option>macvlan:</option> a macvlan interface is linked
472 with the interface specified by
473 the <option>lxc.net.[i].link</option> and assigned to
474 the container.
475 <option>lxc.net.[i].macvlan.mode</option> specifies the
476 mode the macvlan will use to communicate between
477 different macvlan on the same upper device. The accepted
478 modes are <option>private</option>, <option>vepa</option>,
479 <option>bridge</option> and <option>passthru</option>.
480 In <option>private</option> mode, the device never
481 communicates with any other device on the same upper_dev (default).
482 In <option>vepa</option> mode, the new Virtual Ethernet Port
483 Aggregator (VEPA) mode, it assumes that the adjacent
484 bridge returns all frames where both source and
485 destination are local to the macvlan port, i.e. the
486 bridge is set up as a reflective relay. Broadcast
487 frames coming in from the upper_dev get flooded to all
488 macvlan interfaces in VEPA mode, local frames are not
489 delivered locally. In <option>bridge</option> mode, it
490 provides the behavior of a simple bridge between
491 different macvlan interfaces on the same port. Frames
492 from one interface to another one get delivered directly
493 and are not sent out externally. Broadcast frames get
494 flooded to all other bridge ports and to the external
495 interface, but when they come back from a reflective
496 relay, we don't deliver them again. Since we know all
497 the MAC addresses, the macvlan bridge mode does not
498 require learning or STP like the bridge module does. In
499 <option>passthru</option> mode, all frames received by
500 the physical interface are forwarded to the macvlan
501 interface. Only one macvlan interface in <option>passthru</option>
502 mode is possible for one physical interface.
503 </para>
504
505 <para>
506 <option>phys:</option> an already existing interface
507 specified by the <option>lxc.net.[i].link</option> is
508 assigned to the container.
509 </para>
510 </listitem>
511 </varlistentry>
512
513 <varlistentry>
514 <term>
515 <option>lxc.net.[i].flags</option>
516 </term>
517 <listitem>
518 <para>
519 Specify an action to do for the network.
520 </para>
521
522 <para><option>up:</option> activates the interface.
523 </para>
524 </listitem>
525 </varlistentry>
526
527 <varlistentry>
528 <term>
529 <option>lxc.net.[i].link</option>
530 </term>
531 <listitem>
532 <para>
533 Specify the interface to be used for real network traffic.
534 </para>
535 </listitem>
536 </varlistentry>
537
538 <varlistentry>
539 <term>
540 <option>lxc.net.[i].mtu</option>
541 </term>
542 <listitem>
543 <para>
544 Specify the maximum transfer unit for this interface.
545 </para>
546 </listitem>
547 </varlistentry>
548
549 <varlistentry>
550 <term>
551 <option>lxc.net.[i].name</option>
552 </term>
553 <listitem>
554 <para>
555 The interface name is dynamically allocated, but if another name
556 is needed because the configuration files being used by the
557 container use a generic name, eg. eth0, this option will rename
558 the interface in the container.
559 </para>
560 </listitem>
561 </varlistentry>
562
563 <varlistentry>
564 <term>
565 <option>lxc.net.[i].hwaddr</option>
566 </term>
567 <listitem>
568 <para>
569 The interface mac address is dynamically allocated by default to
570 the virtual interface, but in some cases, this is needed to
571 resolve a mac address conflict or to always have the same
572 link-local ipv6 address. Any "x" in address will be replaced by
573 random value, this allows setting hwaddr templates.
574 </para>
575 </listitem>
576 </varlistentry>
577
578 <varlistentry>
579 <term>
580 <option>lxc.net.[i].ipv4.address</option>
581 </term>
582 <listitem>
583 <para>
584 Specify the ipv4 address to assign to the virtualized interface.
585 Several lines specify several ipv4 addresses. The address is in
586 format x.y.z.t/m, eg. 192.168.1.123/24.
587 </para>
588 </listitem>
589 </varlistentry>
590
591 <varlistentry>
592 <term>
593 <option>lxc.net.[i].ipv4.gateway</option>
594 </term>
595 <listitem>
596 <para>
597 Specify the ipv4 address to use as the gateway inside the
598 container. The address is in format x.y.z.t, eg. 192.168.1.123.
599
600 Can also have the special value <option>auto</option>,
601 which means to take the primary address from the bridge
602 interface (as specified by the
603 <option>lxc.net.[i].link</option> option) and use that as
604 the gateway. <option>auto</option> is only available when
605 using the <option>veth</option> and
606 <option>macvlan</option> network types.
607 </para>
608 </listitem>
609 </varlistentry>
610
611 <varlistentry>
612 <term>
613 <option>lxc.net.[i].ipv6.address</option>
614 </term>
615 <listitem>
616 <para>
617 Specify the ipv6 address to assign to the virtualized
618 interface. Several lines specify several ipv6 addresses. The
619 address is in format x::y/m, eg.
620 2003:db8:1:0:214:1234:fe0b:3596/64
621 </para>
622 </listitem>
623 </varlistentry>
624
625 <varlistentry>
626 <term>
627 <option>lxc.net.[i].ipv6.gateway</option>
628 </term>
629 <listitem>
630 <para>
631 Specify the ipv6 address to use as the gateway inside the
632 container. The address is in format x::y, eg. 2003:db8:1:0::1
633
634 Can also have the special value <option>auto</option>,
635 which means to take the primary address from the bridge
636 interface (as specified by the
637 <option>lxc.net.[i].link</option> option) and use that as
638 the gateway. <option>auto</option> is only available when
639 using the <option>veth</option> and
640 <option>macvlan</option> network types.
641 </para>
642 </listitem>
643 </varlistentry>
644
645 <varlistentry>
646 <term>
647 <option>lxc.net.[i].script.up</option>
648 </term>
649 <listitem>
650 <para>
651 Add a configuration option to specify a script to be
652 executed after creating and configuring the network used
653 from the host side.
654 </para>
655
656 <para>
657 In addition to the information available to all hooks. The
658 following information is provided to the script:
659 <itemizedlist>
660 <listitem>
661 <para>
662 LXC_HOOK_TYPE: the hook type. This is either 'up' or 'down'.
663 </para>
664 </listitem>
665
666 <listitem>
667 <para>
668 LXC_HOOK_SECTION: the section type 'net'.
669 </para>
670 </listitem>
671
672 <listitem>
673 <para>
674 LXC_NET_TYPE: the network type. This is one of the valid
675 network types listed here (e.g. 'macvlan', 'veth').
676 </para>
677 </listitem>
678
679 <listitem>
680 <para>
681 LXC_NET_PARENT: the parent device on the host. This is only
682 set for network types 'mavclan', 'veth', 'phys'.
683 </para>
684 </listitem>
685
686 <listitem>
687 <para>
688 LXC_NET_PEER: the name of the peer device on the host. This is
689 only set for 'veth' network types. Note that this information
690 is only available when <option>lxc.hook.version</option> is set
691 to 1.
692 </para>
693 </listitem>
694 </itemizedlist>
695
696 Whether this information is provided in the form of environment
697 variables or as arguments to the script depends on the value of
698 <option>lxc.hook.version</option>. If set to 1 then information is
699 provided in the form of environment variables. If set to 0
700 information is provided as arguments to the script.
701 </para>
702
703 <para>
704 Standard output from the script is logged at debug level.
705 Standard error is not logged, but can be captured by the
706 hook redirecting its standard error to standard output.
707 </para>
708 </listitem>
709 </varlistentry>
710
711 <varlistentry>
712 <term>
713 <option>lxc.net.[i].script.down</option>
714 </term>
715 <listitem>
716 <para>
717 Add a configuration option to specify a script to be
718 executed before destroying the network used from the
719 host side.
720 </para>
721
722 <para>
723 In addition to the information available to all hooks. The
724 following information is provided to the script:
725 <itemizedlist>
726 <listitem>
727 <para>
728 LXC_HOOK_TYPE: the hook type. This is either 'up' or 'down'.
729 </para>
730 </listitem>
731
732 <listitem>
733 <para>
734 LXC_HOOK_SECTION: the section type 'net'.
735 </para>
736 </listitem>
737
738 <listitem>
739 <para>
740 LXC_NET_TYPE: the network type. This is one of the valid
741 network types listed here (e.g. 'macvlan', 'veth').
742 </para>
743 </listitem>
744
745 <listitem>
746 <para>
747 LXC_NET_PARENT: the parent device on the host. This is only
748 set for network types 'mavclan', 'veth', 'phys'.
749 </para>
750 </listitem>
751
752 <listitem>
753 <para>
754 LXC_NET_PEER: the name of the peer device on the host. This is
755 only set for 'veth' network types. Note that this information
756 is only available when <option>lxc.hook.version</option> is set
757 to 1.
758 </para>
759 </listitem>
760 </itemizedlist>
761
762 Whether this information is provided in the form of environment
763 variables or as arguments to the script depends on the value of
764 <option>lxc.hook.version</option>. If set to 1 then information is
765 provided in the form of environment variables. If set to 0
766 information is provided as arguments to the script.
767 </para>
768
769 <para>
770 Standard output from the script is logged at debug level.
771 Standard error is not logged, but can be captured by the
772 hook redirecting its standard error to standard output.
773 </para>
774 </listitem>
775 </varlistentry>
776 </variablelist>
777 </refsect2>
778
779 <refsect2>
780 <title>New pseudo tty instance (devpts)</title>
781 <para>
782 For stricter isolation the container can have its own private
783 instance of the pseudo tty.
784 </para>
785 <variablelist>
786 <varlistentry>
787 <term>
788 <option>lxc.pty.max</option>
789 </term>
790 <listitem>
791 <para>
792 If set, the container will have a new pseudo tty
793 instance, making this private to it. The value specifies
794 the maximum number of pseudo ttys allowed for a pts
795 instance (this limitation is not implemented yet).
796 </para>
797 </listitem>
798 </varlistentry>
799 </variablelist>
800 </refsect2>
801
802 <refsect2>
803 <title>Container system console</title>
804 <para>
805 If the container is configured with a root filesystem and the
806 inittab file is setup to use the console, you may want to specify
807 where the output of this console goes.
808 </para>
809 <variablelist>
810
811 <varlistentry>
812 <term>
813 <option>lxc.console.buffer.size</option>
814 </term>
815 <listitem>
816 <para>
817 Setting this option instructs liblxc to allocate an in-memory
818 ringbuffer. The container's console output will be written to the
819 ringbuffer. Note that ringbuffer must be at least as big as a
820 standard page size. When passed a value smaller than a single page
821 size liblxc will allocate a ringbuffer of a single page size. A page
822 size is usually 4kB.
823
824 The keyword 'auto' will cause liblxc to allocate a ringbuffer of
825 128kB.
826
827 When manually specifying a size for the ringbuffer the value should
828 be a power of 2 when converted to bytes. Valid size prefixes are
829 'kB', 'MB', 'GB'. (Note that all conversions are based on multiples
830 of 1024. That means 'kb' == 'KiB', 'MB' == 'MiB', 'GB' == 'GiB'.)
831 </para>
832 </listitem>
833 </varlistentry>
834
835 <varlistentry>
836 <term>
837 <option>lxc.console.buffer.logfile</option>
838 </term>
839 <listitem>
840 <para>
841 Setting this option instructs liblxc to write the in-memory
842 ringbuffer to disk. For performance reasons liblxc will only write
843 the in-memory ringbuffer to disk when requested. Note that the this
844 option is only used by liblxc when
845 <option>lxc.console.buffer.size</option> is set.
846
847 By default liblxc will dump the contents of the in-memory ringbuffer
848 to disk when the container terminates. This allows users to diagnose
849 boot failures when the container crashed before an API request to
850 retrieve the in-memory ringbuffer could be sent or handled.
851 </para>
852 </listitem>
853 </varlistentry>
854
855 <varlistentry>
856 <term>
857 <option>lxc.console.logfile</option>
858 </term>
859 <listitem>
860 <para>
861 Specify a path to a file where the console output will be written.
862 Note that in contrast to the on-disk ringbuffer logfile this file
863 will keep growing potentially filling up the users disks if not
864 rotated and deleted. This problem can also be avoided by using the
865 in-memory ringbuffer options
866 <option>lxc.console.buffer.size</option> and
867 <option>lxc.console.buffer.logfile</option>.
868 </para>
869 </listitem>
870 </varlistentry>
871
872 <varlistentry>
873 <term>
874 <option>lxc.console.rotate</option>
875 </term>
876 <listitem>
877 <para>
878 Whether to rotate the console logfile specified in
879 <option>lxc.console.logfile</option>. Users can send an API
880 request to rotate the logfile. Note that the old logfile will have
881 the same name as the original with the suffix ".1" appended.
882
883 Users wishing to prevent the console log file from filling the
884 disk should rotate the logfile and delete it if unneeded. This
885 problem can also be avoided by using the in-memory ringbuffer
886 options <option>lxc.console.buffer.size</option> and
887 <option>lxc.console.buffer.logfile</option>.
888 </para>
889 </listitem>
890 </varlistentry>
891
892 <varlistentry>
893 <term>
894 <option>lxc.console.path</option>
895 </term>
896 <listitem>
897 <para>
898 Specify a path to a device to which the console will be
899 attached. The keyword 'none' will simply disable the
900 console. Note, when specifying 'none' and creating a device node
901 for the console in the container at /dev/console or bind-mounting
902 the hosts's /dev/console into the container at /dev/console the
903 container will have direct access to the hosts's /dev/console.
904 This is dangerous when the container has write access to the
905 device and should thus be used with caution.
906 </para>
907 </listitem>
908 </varlistentry>
909 </variablelist>
910 </refsect2>
911
912 <refsect2>
913 <title>Console through the ttys</title>
914 <para>
915 This option is useful if the container is configured with a root
916 filesystem and the inittab file is setup to launch a getty on the
917 ttys. The option specifies the number of ttys to be available for
918 the container. The number of gettys in the inittab file of the
919 container should not be greater than the number of ttys specified
920 in this option, otherwise the excess getty sessions will die and
921 respawn indefinitely giving annoying messages on the console or in
922 <filename>/var/log/messages</filename>.
923 </para>
924 <variablelist>
925 <varlistentry>
926 <term>
927 <option>lxc.tty.max</option>
928 </term>
929 <listitem>
930 <para>
931 Specify the number of tty to make available to the
932 container.
933 </para>
934 </listitem>
935 </varlistentry>
936 </variablelist>
937 </refsect2>
938
939 <refsect2>
940 <title>Console devices location</title>
941 <para>
942 LXC consoles are provided through Unix98 PTYs created on the
943 host and bind-mounted over the expected devices in the container.
944 By default, they are bind-mounted over <filename>/dev/console</filename>
945 and <filename>/dev/ttyN</filename>. This can prevent package upgrades
946 in the guest. Therefore you can specify a directory location (under
947 <filename>/dev</filename> under which LXC will create the files and
948 bind-mount over them. These will then be symbolically linked to
949 <filename>/dev/console</filename> and <filename>/dev/ttyN</filename>.
950 A package upgrade can then succeed as it is able to remove and replace
951 the symbolic links.
952 </para>
953 <variablelist>
954 <varlistentry>
955 <term>
956 <option>lxc.tty.dir</option>
957 </term>
958 <listitem>
959 <para>
960 Specify a directory under <filename>/dev</filename>
961 under which to create the container console devices. Note that LXC
962 will move any bind-mounts or device nodes for /dev/console into
963 this directory.
964 </para>
965 </listitem>
966 </varlistentry>
967 </variablelist>
968 </refsect2>
969
970 <refsect2>
971 <title>/dev directory</title>
972 <para>
973 By default, lxc creates a few symbolic links (fd,stdin,stdout,stderr)
974 in the container's <filename>/dev</filename> directory but does not
975 automatically create device node entries. This allows the container's
976 <filename>/dev</filename> to be set up as needed in the container
977 rootfs. If lxc.autodev is set to 1, then after mounting the container's
978 rootfs LXC will mount a fresh tmpfs under <filename>/dev</filename>
979 (limited to 500k) and fill in a minimal set of initial devices.
980 This is generally required when starting a container containing
981 a "systemd" based "init" but may be optional at other times. Additional
982 devices in the containers /dev directory may be created through the
983 use of the <option>lxc.hook.autodev</option> hook.
984 </para>
985 <variablelist>
986 <varlistentry>
987 <term>
988 <option>lxc.autodev</option>
989 </term>
990 <listitem>
991 <para>
992 Set this to 0 to stop LXC from mounting and populating a minimal
993 <filename>/dev</filename> when starting the container.
994 </para>
995 </listitem>
996 </varlistentry>
997 </variablelist>
998 </refsect2>
999
1000 <refsect2>
1001 <title>Mount points</title>
1002 <para>
1003 The mount points section specifies the different places to be
1004 mounted. These mount points will be private to the container
1005 and won't be visible by the processes running outside of the
1006 container. This is useful to mount /etc, /var or /home for
1007 examples.
1008 </para>
1009 <para>
1010 NOTE - LXC will generally ensure that mount targets and relative
1011 bind-mount sources are properly confined under the container
1012 root, to avoid attacks involving over-mounting host directories
1013 and files. (Symbolic links in absolute mount sources are ignored)
1014 However, if the container configuration first mounts a directory which
1015 is under the control of the container user, such as /home/joe, into
1016 the container at some <filename>path</filename>, and then mounts
1017 under <filename>path</filename>, then a TOCTTOU attack would be
1018 possible where the container user modifies a symbolic link under
1019 his home directory at just the right time.
1020 </para>
1021 <variablelist>
1022 <varlistentry>
1023 <term>
1024 <option>lxc.mount.fstab</option>
1025 </term>
1026 <listitem>
1027 <para>
1028 specify a file location in
1029 the <filename>fstab</filename> format, containing the
1030 mount information. The mount target location can and in
1031 most cases should be a relative path, which will become
1032 relative to the mounted container root. For instance,
1033 </para>
1034 <programlisting>
1035 proc proc proc nodev,noexec,nosuid 0 0
1036 </programlisting>
1037 <para>
1038 Will mount a proc filesystem under the container's /proc,
1039 regardless of where the root filesystem comes from. This
1040 is resilient to block device backed filesystems as well as
1041 container cloning.
1042 </para>
1043 <para>
1044 Note that when mounting a filesystem from an
1045 image file or block device the third field (fs_vfstype)
1046 cannot be auto as with
1047 <citerefentry>
1048 <refentrytitle>mount</refentrytitle>
1049 <manvolnum>8</manvolnum>
1050 </citerefentry>
1051 but must be explicitly specified.
1052 </para>
1053 </listitem>
1054 </varlistentry>
1055
1056 <varlistentry>
1057 <term>
1058 <option>lxc.mount.entry</option>
1059 </term>
1060 <listitem>
1061 <para>
1062 Specify a mount point corresponding to a line in the
1063 fstab format.
1064
1065 Moreover lxc supports mount propagation, such as rslave or
1066 rprivate, and adds three additional mount options.
1067 <option>optional</option> don't fail if mount does not work.
1068 <option>create=dir</option> or <option>create=file</option>
1069 to create dir (or file) when the point will be mounted.
1070 <option>relative</option> source path is taken to be relative to
1071 the mounted container root. For instance,
1072 </para>
1073 <screen>
1074 dev/null proc/kcore none bind,relative 0 0
1075 </screen>
1076 <para>
1077 Will expand dev/null to ${<option>LXC_ROOTFS_MOUNT</option>}/dev/null,
1078 and mount it to proc/kcore inside the container.
1079 </para>
1080 </listitem>
1081 </varlistentry>
1082
1083 <varlistentry>
1084 <term>
1085 <option>lxc.mount.auto</option>
1086 </term>
1087 <listitem>
1088 <para>
1089 specify which standard kernel file systems should be
1090 automatically mounted. This may dramatically simplify
1091 the configuration. The file systems are:
1092 </para>
1093 <itemizedlist>
1094 <listitem>
1095 <para>
1096 <option>proc:mixed</option> (or <option>proc</option>):
1097 mount <filename>/proc</filename> as read-write, but
1098 remount <filename>/proc/sys</filename> and
1099 <filename>/proc/sysrq-trigger</filename> read-only
1100 for security / container isolation purposes.
1101 </para>
1102 </listitem>
1103 <listitem>
1104 <para>
1105 <option>proc:rw</option>: mount
1106 <filename>/proc</filename> as read-write
1107 </para>
1108 </listitem>
1109 <listitem>
1110 <para>
1111 <option>sys:mixed</option> (or <option>sys</option>):
1112 mount <filename>/sys</filename> as read-only but with
1113 /sys/devices/virtual/net writable.
1114 </para>
1115 </listitem>
1116 <listitem>
1117 <para>
1118 <option>sys:ro</option>:
1119 mount <filename>/sys</filename> as read-only
1120 for security / container isolation purposes.
1121 </para>
1122 </listitem>
1123 <listitem>
1124 <para>
1125 <option>sys:rw</option>: mount
1126 <filename>/sys</filename> as read-write
1127 </para>
1128 </listitem>
1129
1130 <listitem>
1131 <para>
1132 <option>cgroup:mixed</option>:
1133 Mount a tmpfs to <filename>/sys/fs/cgroup</filename>,
1134 create directories for all hierarchies to which the container
1135 is added, create subdirectories in those hierarchies with the
1136 name of the cgroup, and bind-mount the container's own cgroup
1137 into that directory. The container will be able to write to
1138 its own cgroup directory, but not the parents, since they will
1139 be remounted read-only.
1140 </para>
1141 </listitem>
1142
1143 <listitem>
1144 <para>
1145 <option>cgroup:mixed:force</option>:
1146 The <option>force</option> option will cause LXC to perform
1147 the cgroup mounts for the container under all circumstances.
1148 Otherwise it is similar to <option>cgroup:mixed</option>.
1149 This is mainly useful when the cgroup namespaces are enabled
1150 where LXC will normally leave mounting cgroups to the init
1151 binary of the container since it is perfectly safe to do so.
1152 </para>
1153 </listitem>
1154
1155 <listitem>
1156 <para>
1157 <option>cgroup:ro</option>:
1158 similar to <option>cgroup:mixed</option>, but everything will
1159 be mounted read-only.
1160 </para>
1161 </listitem>
1162
1163 <listitem>
1164 <para>
1165 <option>cgroup:ro:force</option>:
1166 The <option>force</option> option will cause LXC to perform
1167 the cgroup mounts for the container under all circumstances.
1168 Otherwise it is similar to <option>cgroup:ro</option>.
1169 This is mainly useful when the cgroup namespaces are enabled
1170 where LXC will normally leave mounting cgroups to the init
1171 binary of the container since it is perfectly safe to do so.
1172 </para>
1173 </listitem>
1174
1175 <listitem>
1176 <para>
1177 <option>cgroup:rw</option>: similar to
1178 <option>cgroup:mixed</option>, but everything will be mounted
1179 read-write. Note that the paths leading up to the container's
1180 own cgroup will be writable, but will not be a cgroup
1181 filesystem but just part of the tmpfs of
1182 <filename>/sys/fs/cgroup</filename>
1183 </para>
1184 </listitem>
1185
1186 <listitem>
1187 <para>
1188 <option>cgroup:rw:force</option>:
1189 The <option>force</option> option will cause LXC to perform
1190 the cgroup mounts for the container under all circumstances.
1191 Otherwise it is similar to <option>cgroup:rw</option>.
1192 This is mainly useful when the cgroup namespaces are enabled
1193 where LXC will normally leave mounting cgroups to the init
1194 binary of the container since it is perfectly safe to do so.
1195 </para>
1196 </listitem>
1197
1198 <listitem>
1199 <para>
1200 <option>cgroup</option> (without specifier):
1201 defaults to <option>cgroup:rw</option> if the
1202 container retains the CAP_SYS_ADMIN capability,
1203 <option>cgroup:mixed</option> otherwise.
1204 </para>
1205 </listitem>
1206
1207 <listitem>
1208 <para>
1209 <option>cgroup-full:mixed</option>:
1210 mount a tmpfs to <filename>/sys/fs/cgroup</filename>,
1211 create directories for all hierarchies to which
1212 the container is added, bind-mount the hierarchies
1213 from the host to the container and make everything
1214 read-only except the container's own cgroup. Note
1215 that compared to <option>cgroup</option>, where
1216 all paths leading up to the container's own cgroup
1217 are just simple directories in the underlying
1218 tmpfs, here
1219 <filename>/sys/fs/cgroup/$hierarchy</filename>
1220 will contain the host's full cgroup hierarchy,
1221 albeit read-only outside the container's own cgroup.
1222 This may leak quite a bit of information into the
1223 container.
1224 </para>
1225 </listitem>
1226
1227 <listitem>
1228 <para>
1229 <option>cgroup-full:mixed:force</option>:
1230 The <option>force</option> option will cause LXC to perform
1231 the cgroup mounts for the container under all circumstances.
1232 Otherwise it is similar to <option>cgroup-full:mixed</option>.
1233 This is mainly useful when the cgroup namespaces are enabled
1234 where LXC will normally leave mounting cgroups to the init
1235 binary of the container since it is perfectly safe to do so.
1236 </para>
1237 </listitem>
1238
1239 <listitem>
1240 <para>
1241 <option>cgroup-full:ro</option>: similar to
1242 <option>cgroup-full:mixed</option>, but everything
1243 will be mounted read-only.
1244 </para>
1245 </listitem>
1246
1247 <listitem>
1248 <para>
1249 <option>cgroup-full:ro:force</option>:
1250 The <option>force</option> option will cause LXC to perform
1251 the cgroup mounts for the container under all circumstances.
1252 Otherwise it is similar to <option>cgroup-full:ro</option>.
1253 This is mainly useful when the cgroup namespaces are enabled
1254 where LXC will normally leave mounting cgroups to the init
1255 binary of the container since it is perfectly safe to do so.
1256 </para>
1257 </listitem>
1258
1259 <listitem>
1260 <para>
1261 <option>cgroup-full:rw</option>: similar to
1262 <option>cgroup-full:mixed</option>, but everything
1263 will be mounted read-write. Note that in this case,
1264 the container may escape its own cgroup. (Note also
1265 that if the container has CAP_SYS_ADMIN support
1266 and can mount the cgroup filesystem itself, it may
1267 do so anyway.)
1268 </para>
1269 </listitem>
1270
1271 <listitem>
1272 <para>
1273 <option>cgroup-full:rw:force</option>:
1274 The <option>force</option> option will cause LXC to perform
1275 the cgroup mounts for the container under all circumstances.
1276 Otherwise it is similar to <option>cgroup-full:rw</option>.
1277 This is mainly useful when the cgroup namespaces are enabled
1278 where LXC will normally leave mounting cgroups to the init
1279 binary of the container since it is perfectly safe to do so.
1280 </para>
1281 </listitem>
1282
1283 <listitem>
1284 <para>
1285 <option>cgroup-full</option> (without specifier):
1286 defaults to <option>cgroup-full:rw</option> if the
1287 container retains the CAP_SYS_ADMIN capability,
1288 <option>cgroup-full:mixed</option> otherwise.
1289 </para>
1290 </listitem>
1291
1292 </itemizedlist>
1293 <para>
1294 If cgroup namespaces are enabled, then any <option>cgroup</option>
1295 auto-mounting request will be ignored, since the container can
1296 mount the filesystems itself, and automounting can confuse the
1297 container init.
1298 </para>
1299 <para>
1300 Note that if automatic mounting of the cgroup filesystem
1301 is enabled, the tmpfs under
1302 <filename>/sys/fs/cgroup</filename> will always be
1303 mounted read-write (but for the <option>:mixed</option>
1304 and <option>:ro</option> cases, the individual
1305 hierarchies,
1306 <filename>/sys/fs/cgroup/$hierarchy</filename>, will be
1307 read-only). This is in order to work around a quirk in
1308 Ubuntu's
1309 <citerefentry>
1310 <refentrytitle>mountall</refentrytitle>
1311 <manvolnum>8</manvolnum>
1312 </citerefentry>
1313 command that will cause containers to wait for user
1314 input at boot if
1315 <filename>/sys/fs/cgroup</filename> is mounted read-only
1316 and the container can't remount it read-write due to a
1317 lack of CAP_SYS_ADMIN.
1318 </para>
1319 <para>
1320 Examples:
1321 </para>
1322 <programlisting>
1323 lxc.mount.auto = proc sys cgroup
1324 lxc.mount.auto = proc:rw sys:rw cgroup-full:rw
1325 </programlisting>
1326 </listitem>
1327 </varlistentry>
1328
1329 </variablelist>
1330 </refsect2>
1331
1332 <refsect2>
1333 <title>Root file system</title>
1334 <para>
1335 The root file system of the container can be different than that
1336 of the host system.
1337 </para>
1338 <variablelist>
1339 <varlistentry>
1340 <term>
1341 <option>lxc.rootfs.path</option>
1342 </term>
1343 <listitem>
1344 <para>
1345 specify the root file system for the container. It can
1346 be an image file, a directory or a block device. If not
1347 specified, the container shares its root file system
1348 with the host.
1349 </para>
1350 <para>
1351 For directory or simple block-device backed containers,
1352 a pathname can be used. If the rootfs is backed by a nbd
1353 device, then <filename>nbd:file:1</filename> specifies that
1354 <filename>file</filename> should be attached to a nbd device,
1355 and partition 1 should be mounted as the rootfs.
1356 <filename>nbd:file</filename> specifies that the nbd device
1357 itself should be mounted. <filename>overlayfs:/lower:/upper</filename>
1358 specifies that the rootfs should be an overlay with <filename>/upper</filename>
1359 being mounted read-write over a read-only mount of <filename>/lower</filename>.
1360 <filename>aufs:/lower:/upper</filename> does the same using aufs in place
1361 of overlayfs. For both <filename>overlayfs</filename> and
1362 <filename>aufs</filename> multiple <filename>/lower</filename>
1363 directories can be specified. <filename>loop:/file</filename> tells lxc to attach
1364 <filename>/file</filename> to a loop device and mount the loop device.
1365 </para>
1366 </listitem>
1367 </varlistentry>
1368
1369 <varlistentry>
1370 <term>
1371 <option>lxc.rootfs.mount</option>
1372 </term>
1373 <listitem>
1374 <para>
1375 where to recursively bind <option>lxc.rootfs.path</option>
1376 before pivoting. This is to ensure success of the
1377 <citerefentry>
1378 <refentrytitle><command>pivot_root</command></refentrytitle>
1379 <manvolnum>8</manvolnum>
1380 </citerefentry>
1381 syscall. Any directory suffices, the default should
1382 generally work.
1383 </para>
1384 </listitem>
1385 </varlistentry>
1386
1387 <varlistentry>
1388 <term>
1389 <option>lxc.rootfs.options</option>
1390 </term>
1391 <listitem>
1392 <para>
1393 extra mount options to use when mounting the rootfs.
1394 </para>
1395 </listitem>
1396 </varlistentry>
1397
1398 </variablelist>
1399 </refsect2>
1400
1401 <refsect2>
1402 <title>Control group</title>
1403 <para>
1404 The control group section contains the configuration for the
1405 different subsystem. <command>lxc</command> does not check the
1406 correctness of the subsystem name. This has the disadvantage
1407 of not detecting configuration errors until the container is
1408 started, but has the advantage of permitting any future
1409 subsystem.
1410 </para>
1411 <variablelist>
1412 <varlistentry>
1413 <term>
1414 <option>lxc.cgroup.[controller name]</option>
1415 </term>
1416 <listitem>
1417 <para>
1418 Specify the control group value to be set on a legacy cgroup
1419 hierarchy. The controller name is the literal name of the control
1420 group. The permitted names and the syntax of their values is not
1421 dictated by LXC, instead it depends on the features of the Linux
1422 kernel running at the time the container is started, eg.
1423 <option>lxc.cgroup.cpuset.cpus</option>
1424 </para>
1425 </listitem>
1426 </varlistentry>
1427 <varlistentry>
1428 <term>
1429 <option>lxc.cgroup2.[controller name]</option>
1430 </term>
1431 <listitem>
1432 <para>
1433 Specify the control group value to be set on the unified cgroup
1434 shierarchy. The controller name is the literal name of the control
1435 group. The permitted names and the syntax of their values is not
1436 dictated by LXC, instead it depends on the features of the Linux
1437 kernel running at the time the container is started, eg.
1438 <option>lxc.cgroup2.memory.high</option>
1439 </para>
1440 </listitem>
1441 </varlistentry>
1442 <varlistentry>
1443 <term>
1444 <option>lxc.cgroup.dir</option>
1445 </term>
1446 <listitem>
1447 <para>
1448 specify a directory or path in which the container's cgroup will
1449 be created. For example, setting
1450 <option>lxc.cgroup.dir = my-cgroup/first</option> for a container
1451 named "c1" will create the container's cgroup as a sub-cgroup of
1452 "my-cgroup". For example, if the user's current cgroup "my-user"
1453 is located in the root cgroup of the cpuset controller in a
1454 cgroup v1 hierarchy this would create the cgroup
1455 "/sys/fs/cgroup/cpuset/my-user/my-cgroup/first/c1" for the
1456 container. Any missing cgroups will be created by LXC. This
1457 presupposes that the user has write access to its current cgroup.
1458 </para>
1459 </listitem>
1460 </varlistentry>
1461 </variablelist>
1462 </refsect2>
1463
1464 <refsect2>
1465 <title>Capabilities</title>
1466 <para>
1467 The capabilities can be dropped in the container if this one
1468 is run as root.
1469 </para>
1470 <variablelist>
1471 <varlistentry>
1472 <term>
1473 <option>lxc.cap.drop</option>
1474 </term>
1475 <listitem>
1476 <para>
1477 Specify the capability to be dropped in the container. A
1478 single line defining several capabilities with a space
1479 separation is allowed. The format is the lower case of
1480 the capability definition without the "CAP_" prefix,
1481 eg. CAP_SYS_MODULE should be specified as
1482 sys_module. See
1483 <citerefentry>
1484 <refentrytitle><command>capabilities</command></refentrytitle>
1485 <manvolnum>7</manvolnum>
1486 </citerefentry>.
1487 If used with no value, lxc will clear any drop capabilities
1488 specified up to this point.
1489 </para>
1490 </listitem>
1491 </varlistentry>
1492 <varlistentry>
1493 <term>
1494 <option>lxc.cap.keep</option>
1495 </term>
1496 <listitem>
1497 <para>
1498 Specify the capability to be kept in the container. All other
1499 capabilities will be dropped. When a special value of "none" is
1500 encountered, lxc will clear any keep capabilities specified up
1501 to this point. A value of "none" alone can be used to drop all
1502 capabilities.
1503 </para>
1504 </listitem>
1505 </varlistentry>
1506 </variablelist>
1507 </refsect2>
1508
1509 <refsect2>
1510 <title>Namespaces</title>
1511 <para>
1512 A namespace can be cloned (<option>lxc.namespace.clone</option>),
1513 kept (<option>lxc.namespace.keep</option>) or shared
1514 (<option>lxc.namespace.share.[namespace identifier]</option>).
1515 </para>
1516 <variablelist>
1517 <varlistentry>
1518 <term>
1519 <option>lxc.namespace.clone</option>
1520 </term>
1521 <listitem>
1522 <para>
1523 Specify namespaces which the container is supposed to be created
1524 with. The namespaces to create are specified as a space separated
1525 list. Each namespace must correspond to one of the standard
1526 namespace identifiers as seen in the
1527 <filename>/proc/PID/ns</filename> directory.
1528 When <option>lxc.namespace.clone</option> is not explicitly set all
1529 namespaces supported by the kernel and the current configuration
1530 will be used.
1531 </para>
1532
1533 <para>
1534 To create a new mount, net and ipc namespace set
1535 <option>lxc.namespace.clone=mount net ipc</option>.
1536 </para>
1537 </listitem>
1538 </varlistentry>
1539
1540 <varlistentry>
1541 <term>
1542 <option>lxc.namespace.keep</option>
1543 </term>
1544 <listitem>
1545 <para>
1546 Specify namespaces which the container is supposed to inherit from
1547 the process that created it. The namespaces to keep are specified as
1548 a space separated list. Each namespace must correspond to one of the
1549 standard namespace identifiers as seen in the
1550 <filename>/proc/PID/ns</filename> directory.
1551 The <option>lxc.namespace.keep</option> is a
1552 blacklist option, i.e. it is useful when enforcing that containers
1553 must keep a specific set of namespaces.
1554 </para>
1555
1556 <para>
1557 To keep the network, user and ipc namespace set
1558 <option>lxc.namespace.keep=user net ipc</option>.
1559 </para>
1560
1561 <para>
1562 Note that sharing pid namespaces will likely not work with most init
1563 systems.
1564 </para>
1565
1566 <para>
1567 Note that if the container requests a new user namespace and the
1568 container wants to inherit the network namespace it needs to inherit
1569 the user namespace as well.
1570 </para>
1571 </listitem>
1572 </varlistentry>
1573
1574 <varlistentry>
1575 <term>
1576 <option>lxc.namespace.share.[namespace identifier]</option>
1577 </term>
1578 <listitem>
1579 <para>
1580 Specify a namespace to inherit from another container or process.
1581 The <option>[namespace identifier]</option> suffix needs to be
1582 replaced with one of the namespaces that appear in the
1583 <filename>/proc/PID/ns</filename> directory.
1584 </para>
1585
1586 <para>
1587 To inherit the namespace from another process set the
1588 <option>lxc.namespace.share.[namespace identifier]</option> to the PID of
1589 the process, e.g. <option>lxc.namespace.share.net=42</option>.
1590 </para>
1591
1592 <para>
1593 To inherit the namespace from another container set the
1594 <option>lxc.namespace.share.[namespace identifier]</option> to the name of
1595 the container, e.g. <option>lxc.namespace.share.pid=c3</option>.
1596 </para>
1597
1598 <para>
1599 To inherit the namespace from another container located in a
1600 different path than the standard liblxc path set the
1601 <option>lxc.namespace.share.[namespace identifier]</option> to the full
1602 path to the container, e.g.
1603 <option>lxc.namespace.share.user=/opt/c3</option>.
1604 </para>
1605
1606 <para>
1607 In order to inherit namespaces the caller needs to have sufficient
1608 privilege over the process or container.
1609 </para>
1610
1611 <para>
1612 Note that sharing pid namespaces between system containers will
1613 likely not work with most init systems.
1614 </para>
1615
1616 <para>
1617 Note that if two processes are in different user namespaces and one
1618 process wants to inherit the other's network namespace it usually
1619 needs to inherit the user namespace as well.
1620 </para>
1621 </listitem>
1622 </varlistentry>
1623 </variablelist>
1624 </refsect2>
1625
1626 <refsect2>
1627 <title>Resource limits</title>
1628 <para>
1629 The soft and hard resource limits for the container can be changed.
1630 Unprivileged containers can only lower them. Resources which are not
1631 explicitly specified will be inherited.
1632 </para>
1633 <variablelist>
1634 <varlistentry>
1635 <term>
1636 <option>lxc.prlimit.[limit name]</option>
1637 </term>
1638 <listitem>
1639 <para>
1640 Specify the resource limit to be set. A limit is specified as two
1641 colon separated values which are either numeric or the word
1642 'unlimited'. A single value can be used as a shortcut to set both
1643 soft and hard limit to the same value. The permitted names the
1644 "RLIMIT_" resource names in lowercase without the "RLIMIT_"
1645 prefix, eg. RLIMIT_NOFILE should be specified as "nofile". See
1646 <citerefentry>
1647 <refentrytitle><command>setrlimit</command></refentrytitle>
1648 <manvolnum>2</manvolnum>
1649 </citerefentry>.
1650 If used with no value, lxc will clear the resource limit
1651 specified up to this point. A resource with no explicitly
1652 configured limitation will be inherited from the process starting
1653 up the container.
1654 </para>
1655 </listitem>
1656 </varlistentry>
1657 </variablelist>
1658 </refsect2>
1659
1660 <refsect2>
1661 <title>Sysctl</title>
1662 <para>
1663 Configure kernel parameters for the container.
1664 </para>
1665 <variablelist>
1666 <varlistentry>
1667 <term>
1668 <option>lxc.sysctl.[kernel parameters name]</option>
1669 </term>
1670 <listitem>
1671 <para>
1672 Specify the kernel parameters to be set. The parameters available
1673 are those listed under /proc/sys/.
1674 Note that not all sysctls are namespaced. Changing Non-namespaced
1675 sysctls will cause the system-wide setting to be modified.
1676 <citerefentry>
1677 <refentrytitle><command>sysctl</command></refentrytitle>
1678 <manvolnum>8</manvolnum>
1679 </citerefentry>.
1680 If used with no value, lxc will clear the parameters specified up
1681 to this point.
1682 </para>
1683 </listitem>
1684 </varlistentry>
1685 </variablelist>
1686 </refsect2>
1687
1688 <refsect2>
1689 <title>Apparmor profile</title>
1690 <para>
1691 If lxc was compiled and installed with apparmor support, and the host
1692 system has apparmor enabled, then the apparmor profile under which the
1693 container should be run can be specified in the container
1694 configuration. The default is <command>lxc-container-default-cgns</command>
1695 if the host kernel is cgroup namespace aware, or
1696 <command>lxc-container-default</command> othewise.
1697 </para>
1698 <variablelist>
1699 <varlistentry>
1700 <term>
1701 <option>lxc.apparmor.profile</option>
1702 </term>
1703 <listitem>
1704 <para>
1705 Specify the apparmor profile under which the container should
1706 be run. To specify that the container should be unconfined,
1707 use
1708 </para>
1709 <programlisting>lxc.apparmor.profile = unconfined</programlisting>
1710 <para>
1711 If the apparmor profile should remain unchanged (i.e. if you
1712 are nesting containers and are already confined), then use
1713 </para>
1714 <programlisting>lxc.apparmor.profile = unchanged</programlisting>
1715 </listitem>
1716 </varlistentry>
1717 <varlistentry>
1718 <term>
1719 <option>lxc.apparmor.allow_incomplete</option>
1720 </term>
1721 <listitem>
1722 <para>
1723 Apparmor profiles are pathname based. Therefore many file
1724 restrictions require mount restrictions to be effective against
1725 a determined attacker. However, these mount restrictions are not
1726 yet implemented in the upstream kernel. Without the mount
1727 restrictions, the apparmor profiles still protect against accidental
1728 damager.
1729 </para>
1730 <para>
1731 If this flag is 0 (default), then the container will not be
1732 started if the kernel lacks the apparmor mount features, so that a
1733 regression after a kernel upgrade will be detected. To start the
1734 container under partial apparmor protection, set this flag to 1.
1735 </para>
1736 </listitem>
1737 </varlistentry>
1738 </variablelist>
1739 </refsect2>
1740
1741 <refsect2>
1742 <title>SELinux context</title>
1743 <para>
1744 If lxc was compiled and installed with SELinux support, and the host
1745 system has SELinux enabled, then the SELinux context under which the
1746 container should be run can be specified in the container
1747 configuration. The default is <command>unconfined_t</command>,
1748 which means that lxc will not attempt to change contexts.
1749 See @DATADIR@/lxc/selinux/lxc.te for an example policy and more
1750 information.
1751 </para>
1752 <variablelist>
1753 <varlistentry>
1754 <term>
1755 <option>lxc.selinux.context</option>
1756 </term>
1757 <listitem>
1758 <para>
1759 Specify the SELinux context under which the container should
1760 be run or <command>unconfined_t</command>. For example
1761 </para>
1762 <programlisting>lxc.selinux.context = system_u:system_r:lxc_t:s0:c22</programlisting>
1763 </listitem>
1764 </varlistentry>
1765 </variablelist>
1766 </refsect2>
1767
1768 <refsect2>
1769 <title>Seccomp configuration</title>
1770 <para>
1771 A container can be started with a reduced set of available
1772 system calls by loading a seccomp profile at startup. The
1773 seccomp configuration file must begin with a version number
1774 on the first line, a policy type on the second line, followed
1775 by the configuration.
1776 </para>
1777 <para>
1778 Versions 1 and 2 are currently supported. In version 1, the
1779 policy is a simple whitelist. The second line therefore must
1780 read "whitelist", with the rest of the file containing one (numeric)
1781 sycall number per line. Each syscall number is whitelisted,
1782 while every unlisted number is blacklisted for use in the container
1783 </para>
1784
1785 <para>
1786 In version 2, the policy may be blacklist or whitelist,
1787 supports per-rule and per-policy default actions, and supports
1788 per-architecture system call resolution from textual names.
1789 </para>
1790 <para>
1791 An example blacklist policy, in which all system calls are
1792 allowed except for mknod, which will simply do nothing and
1793 return 0 (success), looks like:
1794 </para>
1795
1796 <programlisting>
1797 2
1798 blacklist
1799 mknod errno 0
1800 </programlisting>
1801
1802 <variablelist>
1803 <varlistentry>
1804 <term>
1805 <option>lxc.seccomp.profile</option>
1806 </term>
1807 <listitem>
1808 <para>
1809 Specify a file containing the seccomp configuration to
1810 load before the container starts.
1811 </para>
1812 </listitem>
1813 </varlistentry>
1814 </variablelist>
1815 </refsect2>
1816
1817 <refsect2>
1818 <title>PR_SET_NO_NEW_PRIVS</title>
1819 <para>
1820 With PR_SET_NO_NEW_PRIVS active execve() promises not to grant
1821 privileges to do anything that could not have been done without
1822 the execve() call (for example, rendering the set-user-ID and
1823 set-group-ID mode bits, and file capabilities non-functional).
1824 Once set, this bit cannot be unset. The setting of this bit is
1825 inherited by children created by fork() and clone(), and preserved
1826 across execve().
1827 Note that PR_SET_NO_NEW_PRIVS is applied after the container has
1828 changed into its intended AppArmor profile or SElinux context.
1829 </para>
1830 <variablelist>
1831 <varlistentry>
1832 <term>
1833 <option>lxc.no_new_privs</option>
1834 </term>
1835 <listitem>
1836 <para>
1837 Specify whether the PR_SET_NO_NEW_PRIVS flag should be set for the
1838 container. Set to 1 to activate.
1839 </para>
1840 </listitem>
1841 </varlistentry>
1842 </variablelist>
1843 </refsect2>
1844
1845 <refsect2>
1846 <title>UID mappings</title>
1847 <para>
1848 A container can be started in a private user namespace with
1849 user and group id mappings. For instance, you can map userid
1850 0 in the container to userid 200000 on the host. The root
1851 user in the container will be privileged in the container,
1852 but unprivileged on the host. Normally a system container
1853 will want a range of ids, so you would map, for instance,
1854 user and group ids 0 through 20,000 in the container to the
1855 ids 200,000 through 220,000.
1856 </para>
1857 <variablelist>
1858 <varlistentry>
1859 <term>
1860 <option>lxc.idmap</option>
1861 </term>
1862 <listitem>
1863 <para>
1864 Four values must be provided. First a character, either
1865 'u', or 'g', to specify whether user or group ids are
1866 being mapped. Next is the first userid as seen in the
1867 user namespace of the container. Next is the userid as
1868 seen on the host. Finally, a range indicating the number
1869 of consecutive ids to map.
1870 </para>
1871 </listitem>
1872 </varlistentry>
1873 </variablelist>
1874 </refsect2>
1875
1876 <refsect2>
1877 <title>Container hooks</title>
1878 <para>
1879 Container hooks are programs or scripts which can be executed
1880 at various times in a container's lifetime.
1881 </para>
1882 <para>
1883 When a container hook is executed, additional information is passed
1884 along. The <option>lxc.hook.version</option> argument can be used to
1885 determine if the following arguments are passed as command line
1886 arguments or through environment variables. The arguments are:
1887 <itemizedlist>
1888 <listitem><para> Container name. </para></listitem>
1889 <listitem><para> Section (always 'lxc'). </para></listitem>
1890 <listitem><para> The hook type (i.e. 'clone' or 'pre-mount'). </para></listitem>
1891 <listitem><para> Additional arguments. In the
1892 case of the clone hook, any extra arguments passed to
1893 lxc-clone will appear as further arguments to the hook.
1894 In the case of the stop hook, paths to filedescriptors
1895 for each of the container's namespaces along with their types
1896 are passed. </para></listitem>
1897 </itemizedlist>
1898 The following environment variables are set:
1899 <itemizedlist>
1900 <listitem><para> LXC_CGNS_AWARE: indicator whether the container is
1901 cgroup namespace aware. </para></listitem>
1902 <listitem><para> LXC_CONFIG_FILE: the path to the container
1903 configuration file. </para></listitem>
1904 <listitem><para> LXC_HOOK_TYPE: the hook type (e.g. 'clone', 'mount',
1905 'pre-mount'). Note that the existence of this environment variable is
1906 conditional on the value of <option>lxc.hook.version</option>. If it
1907 is set to 1 then LXC_HOOK_TYPE will be set.
1908 </para></listitem>
1909 <listitem><para> LXC_HOOK_SECTION: the section type (e.g. 'lxc',
1910 'net'). Note that the existence of this environment variable is
1911 conditional on the value of <option>lxc.hook.version</option>. If it
1912 is set to 1 then LXC_HOOK_SECTION will be set.
1913 </para></listitem>
1914 <listitem><para> LXC_HOOK_VERSION: the version of the hooks. This
1915 value is identical to the value of the container's
1916 <option>lxc.hook.version</option> config item. If it is set to 0 then
1917 old-style hooks are used. If it is set to 1 then new-style hooks are
1918 used. </para></listitem>
1919 <listitem><para> LXC_LOG_LEVEL: the container's log level. </para></listitem>
1920 <listitem><para> LXC_NAME: is the container's name. </para></listitem>
1921 <listitem><para> LXC_[NAMESPACE IDENTIFIER]_NS: path under
1922 /proc/PID/fd/ to a file descriptor referring to the container's
1923 namespace. For each preserved namespace type there will be a separate
1924 environment variable. These environment variables will only be set if
1925 <option>lxc.hook.version</option> is set to 1. </para></listitem>
1926 <listitem><para> LXC_ROOTFS_MOUNT: the path to the mounted root filesystem. </para></listitem>
1927 <listitem><para> LXC_ROOTFS_PATH: this is the lxc.rootfs.path entry
1928 for the container. Note this is likely not where the mounted rootfs is
1929 to be found, use LXC_ROOTFS_MOUNT for that. </para></listitem>
1930 <listitem><para> LXC_SRC_NAME: in the case of the clone hook, this is
1931 the original container's name. </para></listitem>
1932 </itemizedlist>
1933 </para>
1934 <para>
1935 Standard output from the hooks is logged at debug level.
1936 Standard error is not logged, but can be captured by the
1937 hook redirecting its standard error to standard output.
1938 </para>
1939 <variablelist>
1940 <varlistentry>
1941 <term>
1942 <option>lxc.hook.version</option>
1943 </term>
1944 <listitem>
1945 <para>
1946 To pass the arguments in new style via environment variables set to
1947 1 otherwise set to 0 to pass them as arguments.
1948 This setting affects all hooks arguments that were traditionally
1949 passed as arguments to the script. Specifically, it affects the
1950 container name, section (e.g. 'lxc', 'net') and hook type (e.g.
1951 'clone', 'mount', 'pre-mount') arguments. If new-style hooks are
1952 used then the arguments will be available as environment variables.
1953 The container name will be set in LXC_NAME. (This is set
1954 independently of the value used for this config item.) The section
1955 will be set in LXC_HOOK_SECTION and the hook type will be set in
1956 LXC_HOOK_TYPE.
1957 It also affects how the paths to file descriptors referring to the
1958 container's namespaces are passed. If set to 1 then for each
1959 namespace a separate environment variable LXC_[NAMESPACE
1960 IDENTIFIER]_NS will be set. If set to 0 then the paths will be
1961 passed as arguments to the stop hook.
1962 </para>
1963 </listitem>
1964 </varlistentry>
1965 </variablelist>
1966 <variablelist>
1967 <varlistentry>
1968 <term>
1969 <option>lxc.hook.pre-start</option>
1970 </term>
1971 <listitem>
1972 <para>
1973 A hook to be run in the host's namespace before the
1974 container ttys, consoles, or mounts are up.
1975 </para>
1976 </listitem>
1977 </varlistentry>
1978 </variablelist>
1979 <variablelist>
1980 <varlistentry>
1981 <term>
1982 <option>lxc.hook.pre-mount</option>
1983 </term>
1984 <listitem>
1985 <para>
1986 A hook to be run in the container's fs namespace but before
1987 the rootfs has been set up. This allows for manipulation
1988 of the rootfs, i.e. to mount an encrypted filesystem. Mounts
1989 done in this hook will not be reflected on the host (apart from
1990 mounts propagation), so they will be automatically cleaned up
1991 when the container shuts down.
1992 </para>
1993 </listitem>
1994 </varlistentry>
1995 </variablelist>
1996 <variablelist>
1997 <varlistentry>
1998 <term>
1999 <option>lxc.hook.mount</option>
2000 </term>
2001 <listitem>
2002 <para>
2003 A hook to be run in the container's namespace after
2004 mounting has been done, but before the pivot_root.
2005 </para>
2006 </listitem>
2007 </varlistentry>
2008 </variablelist>
2009 <variablelist>
2010 <varlistentry>
2011 <term>
2012 <option>lxc.hook.autodev</option>
2013 </term>
2014 <listitem>
2015 <para>
2016 A hook to be run in the container's namespace after
2017 mounting has been done and after any mount hooks have
2018 run, but before the pivot_root, if
2019 <option>lxc.autodev</option> == 1.
2020 The purpose of this hook is to assist in populating the
2021 /dev directory of the container when using the autodev
2022 option for systemd based containers. The container's /dev
2023 directory is relative to the
2024 ${<option>LXC_ROOTFS_MOUNT</option>} environment
2025 variable available when the hook is run.
2026 </para>
2027 </listitem>
2028 </varlistentry>
2029 </variablelist>
2030 <variablelist>
2031 <varlistentry>
2032 <term>
2033 <option>lxc.hook.start-host</option>
2034 </term>
2035 <listitem>
2036 <para>
2037 A hook to be run in the host's namespace after the
2038 container has been setup, and immediately before starting
2039 the container init.
2040 </para>
2041 </listitem>
2042 </varlistentry>
2043 </variablelist>
2044 <variablelist>
2045 <varlistentry>
2046 <term>
2047 <option>lxc.hook.start</option>
2048 </term>
2049 <listitem>
2050 <para>
2051 A hook to be run in the container's namespace immediately
2052 before executing the container's init. This requires the
2053 program to be available in the container.
2054 </para>
2055 </listitem>
2056 </varlistentry>
2057 </variablelist>
2058 <variablelist>
2059 <varlistentry>
2060 <term>
2061 <option>lxc.hook.stop</option>
2062 </term>
2063 <listitem>
2064 <para>
2065 A hook to be run in the host's namespace with references
2066 to the container's namespaces after the container has been shut
2067 down. For each namespace an extra argument is passed to the hook
2068 containing the namespace's type and a filename that can be used to
2069 obtain a file descriptor to the corresponding namespace, separated
2070 by a colon. The type is the name as it would appear in the
2071 <filename>/proc/PID/ns</filename> directory.
2072 For instance for the mount namespace the argument usually looks
2073 like <filename>mnt:/proc/PID/fd/12</filename>.
2074 </para>
2075 </listitem>
2076 </varlistentry>
2077 </variablelist>
2078 <variablelist>
2079 <varlistentry>
2080 <term>
2081 <option>lxc.hook.post-stop</option>
2082 </term>
2083 <listitem>
2084 <para>
2085 A hook to be run in the host's namespace after the
2086 container has been shut down.
2087 </para>
2088 </listitem>
2089 </varlistentry>
2090 </variablelist>
2091 <variablelist>
2092 <varlistentry>
2093 <term>
2094 <option>lxc.hook.clone</option>
2095 </term>
2096 <listitem>
2097 <para>
2098 A hook to be run when the container is cloned to a new one.
2099 See <citerefentry><refentrytitle><command>lxc-clone</command></refentrytitle>
2100 <manvolnum>1</manvolnum></citerefentry> for more information.
2101 </para>
2102 </listitem>
2103 </varlistentry>
2104 </variablelist>
2105 <variablelist>
2106 <varlistentry>
2107 <term>
2108 <option>lxc.hook.destroy</option>
2109 </term>
2110 <listitem>
2111 <para>
2112 A hook to be run when the container is destroyed.
2113 </para>
2114 </listitem>
2115 </varlistentry>
2116 </variablelist>
2117 </refsect2>
2118
2119 <refsect2>
2120 <title>Container hooks Environment Variables</title>
2121 <para>
2122 A number of environment variables are made available to the startup
2123 hooks to provide configuration information and assist in the
2124 functioning of the hooks. Not all variables are valid in all
2125 contexts. In particular, all paths are relative to the host system
2126 and, as such, not valid during the <option>lxc.hook.start</option> hook.
2127 </para>
2128 <variablelist>
2129 <varlistentry>
2130 <term>
2131 <option>LXC_NAME</option>
2132 </term>
2133 <listitem>
2134 <para>
2135 The LXC name of the container. Useful for logging messages
2136 in common log environments. [<option>-n</option>]
2137 </para>
2138 </listitem>
2139 </varlistentry>
2140 </variablelist>
2141 <variablelist>
2142 <varlistentry>
2143 <term>
2144 <option>LXC_CONFIG_FILE</option>
2145 </term>
2146 <listitem>
2147 <para>
2148 Host relative path to the container configuration file. This
2149 gives the container to reference the original, top level,
2150 configuration file for the container in order to locate any
2151 additional configuration information not otherwise made
2152 available. [<option>-f</option>]
2153 </para>
2154 </listitem>
2155 </varlistentry>
2156 </variablelist>
2157 <variablelist>
2158 <varlistentry>
2159 <term>
2160 <option>LXC_CONSOLE</option>
2161 </term>
2162 <listitem>
2163 <para>
2164 The path to the console output of the container if not NULL.
2165 [<option>-c</option>] [<option>lxc.console.path</option>]
2166 </para>
2167 </listitem>
2168 </varlistentry>
2169 </variablelist>
2170 <variablelist>
2171 <varlistentry>
2172 <term>
2173 <option>LXC_CONSOLE_LOGPATH</option>
2174 </term>
2175 <listitem>
2176 <para>
2177 The path to the console log output of the container if not NULL.
2178 [<option>-L</option>]
2179 </para>
2180 </listitem>
2181 </varlistentry>
2182 </variablelist>
2183 <variablelist>
2184 <varlistentry>
2185 <term>
2186 <option>LXC_ROOTFS_MOUNT</option>
2187 </term>
2188 <listitem>
2189 <para>
2190 The mount location to which the container is initially bound.
2191 This will be the host relative path to the container rootfs
2192 for the container instance being started and is where changes
2193 should be made for that instance.
2194 [<option>lxc.rootfs.mount</option>]
2195 </para>
2196 </listitem>
2197 </varlistentry>
2198 </variablelist>
2199 <variablelist>
2200 <varlistentry>
2201 <term>
2202 <option>LXC_ROOTFS_PATH</option>
2203 </term>
2204 <listitem>
2205 <para>
2206 The host relative path to the container root which has been
2207 mounted to the rootfs.mount location.
2208 [<option>lxc.rootfs.path</option>]
2209 </para>
2210 </listitem>
2211 </varlistentry>
2212 </variablelist>
2213 <variablelist>
2214 <varlistentry>
2215 <term>
2216 <option>LXC_SRC_NAME</option>
2217 </term>
2218 <listitem>
2219 <para>
2220 Only for the clone hook. Is set to the original container name.
2221 </para>
2222 </listitem>
2223 </varlistentry>
2224 </variablelist>
2225 <variablelist>
2226 <varlistentry>
2227 <term>
2228 <option>LXC_TARGET</option>
2229 </term>
2230 <listitem>
2231 <para>
2232 Only for the stop hook. Is set to "stop" for a container
2233 shutdown or "reboot" for a container reboot.
2234 </para>
2235 </listitem>
2236 </varlistentry>
2237 </variablelist>
2238 <variablelist>
2239 <varlistentry>
2240 <term>
2241 <option>LXC_CGNS_AWARE</option>
2242 </term>
2243 <listitem>
2244 <para>
2245 If unset, then this version of lxc is not aware of cgroup
2246 namespaces. If set, it will be set to 1, and lxc is aware
2247 of cgroup namespaces. Note this does not guarantee that
2248 cgroup namespaces are enabled in the kernel. This is used
2249 by the lxcfs mount hook.
2250 </para>
2251 </listitem>
2252 </varlistentry>
2253 </variablelist>
2254 </refsect2>
2255 <refsect2>
2256 <title>Logging</title>
2257 <para>
2258 Logging can be configured on a per-container basis. By default,
2259 depending upon how the lxc package was compiled, container startup
2260 is logged only at the ERROR level, and logged to a file named after
2261 the container (with '.log' appended) either under the container path,
2262 or under @LOGPATH@.
2263 </para>
2264 <para>
2265 Both the default log level and the log file can be specified in the
2266 container configuration file, overriding the default behavior. Note
2267 that the configuration file entries can in turn be overridden by the
2268 command line options to <command>lxc-start</command>.
2269 </para>
2270 <variablelist>
2271 <varlistentry>
2272 <term>
2273 <option>lxc.log.level</option>
2274 </term>
2275 <listitem>
2276 <para>
2277 The level at which to log. The log level is an integer in
2278 the range of 0..8 inclusive, where a lower number means more
2279 verbose debugging. In particular 0 = trace, 1 = debug, 2 =
2280 info, 3 = notice, 4 = warn, 5 = error, 6 = critical, 7 =
2281 alert, and 8 = fatal. If unspecified, the level defaults
2282 to 5 (error), so that only errors and above are logged.
2283 </para>
2284 <para>
2285 Note that when a script (such as either a hook script or a
2286 network interface up or down script) is called, the script's
2287 standard output is logged at level 1, debug.
2288 </para>
2289 </listitem>
2290 </varlistentry>
2291 <varlistentry>
2292 <term>
2293 <option>lxc.log.file</option>
2294 </term>
2295 <listitem>
2296 <para>
2297 The file to which logging info should be written.
2298 </para>
2299 </listitem>
2300 </varlistentry>
2301 <varlistentry>
2302 <term>
2303 <option>lxc.log.syslog</option>
2304 </term>
2305 <listitem>
2306 <para>
2307 Send logging info to syslog. It respects the log level defined in
2308 <command>lxc.log.level</command>. The argument should be the syslog
2309 facility to use, valid ones are: daemon, local0, local1, local2,
2310 local3, local4, local5, local5, local6, local7.
2311 </para>
2312 </listitem>
2313 </varlistentry>
2314 </variablelist>
2315 </refsect2>
2316
2317 <refsect2>
2318 <title>Autostart</title>
2319 <para>
2320 The autostart options support marking which containers should be
2321 auto-started and in what order. These options may be used by LXC tools
2322 directly or by external tooling provided by the distributions.
2323 </para>
2324
2325 <variablelist>
2326 <varlistentry>
2327 <term>
2328 <option>lxc.start.auto</option>
2329 </term>
2330 <listitem>
2331 <para>
2332 Whether the container should be auto-started.
2333 Valid values are 0 (off) and 1 (on).
2334 </para>
2335 </listitem>
2336 </varlistentry>
2337 <varlistentry>
2338 <term>
2339 <option>lxc.start.delay</option>
2340 </term>
2341 <listitem>
2342 <para>
2343 How long to wait (in seconds) after the container is
2344 started before starting the next one.
2345 </para>
2346 </listitem>
2347 </varlistentry>
2348 <varlistentry>
2349 <term>
2350 <option>lxc.start.order</option>
2351 </term>
2352 <listitem>
2353 <para>
2354 An integer used to sort the containers when auto-starting
2355 a series of containers at once.
2356 </para>
2357 </listitem>
2358 </varlistentry>
2359 <varlistentry>
2360 <term>
2361 <option>lxc.monitor.unshare</option>
2362 </term>
2363 <listitem>
2364 <para>
2365 If not zero the mount namespace will be unshared from the host
2366 before initializing the container (before running any pre-start
2367 hooks). This requires the CAP_SYS_ADMIN capability at startup.
2368 Default is 0.
2369 </para>
2370 </listitem>
2371 </varlistentry>
2372 <varlistentry>
2373 <term>
2374 <option>lxc.group</option>
2375 </term>
2376 <listitem>
2377 <para>
2378 A multi-value key (can be used multiple times) to put the
2379 container in a container group. Those groups can then be
2380 used (amongst other things) to start a series of related
2381 containers.
2382 </para>
2383 </listitem>
2384 </varlistentry>
2385 </variablelist>
2386 </refsect2>
2387
2388 <refsect2>
2389 <title>Autostart and System Boot</title>
2390 <para>
2391 Each container can be part of any number of groups or no group at all.
2392 Two groups are special. One is the NULL group, i.e. the container does
2393 not belong to any group. The other group is the "onboot" group.
2394 </para>
2395
2396 <para>
2397 When the system boots with the LXC service enabled, it will first
2398 attempt to boot any containers with lxc.start.auto == 1 that is a member
2399 of the "onboot" group. The startup will be in order of lxc.start.order.
2400 If an lxc.start.delay has been specified, that delay will be honored
2401 before attempting to start the next container to give the current
2402 container time to begin initialization and reduce overloading the host
2403 system. After starting the members of the "onboot" group, the LXC system
2404 will proceed to boot containers with lxc.start.auto == 1 which are not
2405 members of any group (the NULL group) and proceed as with the onboot
2406 group.
2407 </para>
2408
2409 </refsect2>
2410
2411 <refsect2>
2412 <title>Container Environment</title>
2413 <para>
2414 If you want to pass environment variables into the container (that
2415 is, environment variables which will be available to init and all of
2416 its descendents), you can use <command>lxc.environment</command>
2417 parameters to do so. Be careful that you do not pass in anything
2418 sensitive; any process in the container which doesn't have its
2419 environment scrubbed will have these variables available to it, and
2420 environment variables are always available via
2421 <command>/proc/PID/environ</command>.
2422 </para>
2423
2424 <para>
2425 This configuration parameter can be specified multiple times; once
2426 for each environment variable you wish to configure.
2427 </para>
2428
2429 <variablelist>
2430 <varlistentry>
2431 <term>
2432 <option>lxc.environment</option>
2433 </term>
2434 <listitem>
2435 <para>
2436 Specify an environment variable to pass into the container.
2437 Example:
2438 </para>
2439 <programlisting>
2440 lxc.environment = APP_ENV=production
2441 lxc.environment = SYSLOG_SERVER=192.0.2.42
2442 </programlisting>
2443 </listitem>
2444 </varlistentry>
2445 </variablelist>
2446 </refsect2>
2447
2448 </refsect1>
2449
2450 <refsect1>
2451 <title>Examples</title>
2452 <para>
2453 In addition to the few examples given below, you will find
2454 some other examples of configuration file in @DOCDIR@/examples
2455 </para>
2456 <refsect2>
2457 <title>Network</title>
2458 <para>This configuration sets up a container to use a veth pair
2459 device with one side plugged to a bridge br0 (which has been
2460 configured before on the system by the administrator). The
2461 virtual network device visible in the container is renamed to
2462 eth0.</para>
2463 <programlisting>
2464 lxc.uts.name = myhostname
2465 lxc.net.0.type = veth
2466 lxc.net.0.flags = up
2467 lxc.net.0.link = br0
2468 lxc.net.0.name = eth0
2469 lxc.net.0.hwaddr = 4a:49:43:49:79:bf
2470 lxc.net.0.ipv4.address = 10.2.3.5/24 10.2.3.255
2471 lxc.net.0.ipv6.address = 2003:db8:1:0:214:1234:fe0b:3597
2472 </programlisting>
2473 </refsect2>
2474
2475 <refsect2>
2476 <title>UID/GID mapping</title>
2477 <para>This configuration will map both user and group ids in the
2478 range 0-9999 in the container to the ids 100000-109999 on the host.
2479 </para>
2480 <programlisting>
2481 lxc.idmap = u 0 100000 10000
2482 lxc.idmap = g 0 100000 10000
2483 </programlisting>
2484 </refsect2>
2485
2486 <refsect2>
2487 <title>Control group</title>
2488 <para>This configuration will setup several control groups for
2489 the application, cpuset.cpus restricts usage of the defined cpu,
2490 cpus.share prioritize the control group, devices.allow makes
2491 usable the specified devices.</para>
2492 <programlisting>
2493 lxc.cgroup.cpuset.cpus = 0,1
2494 lxc.cgroup.cpu.shares = 1234
2495 lxc.cgroup.devices.deny = a
2496 lxc.cgroup.devices.allow = c 1:3 rw
2497 lxc.cgroup.devices.allow = b 8:0 rw
2498 </programlisting>
2499 </refsect2>
2500
2501 <refsect2>
2502 <title>Complex configuration</title>
2503 <para>This example show a complex configuration making a complex
2504 network stack, using the control groups, setting a new hostname,
2505 mounting some locations and a changing root file system.</para>
2506 <programlisting>
2507 lxc.uts.name = complex
2508 lxc.net.0.type = veth
2509 lxc.net.0.flags = up
2510 lxc.net.0.link = br0
2511 lxc.net.0.hwaddr = 4a:49:43:49:79:bf
2512 lxc.net.0.ipv4.address = 10.2.3.5/24 10.2.3.255
2513 lxc.net.0.ipv6.address = 2003:db8:1:0:214:1234:fe0b:3597
2514 lxc.net.0.ipv6.address = 2003:db8:1:0:214:5432:feab:3588
2515 lxc.net.1.type = macvlan
2516 lxc.net.1.flags = up
2517 lxc.net.1.link = eth0
2518 lxc.net.1.hwaddr = 4a:49:43:49:79:bd
2519 lxc.net.1.ipv4.address = 10.2.3.4/24
2520 lxc.net.1.ipv4.address = 192.168.10.125/24
2521 lxc.net.1.ipv6.address = 2003:db8:1:0:214:1234:fe0b:3596
2522 lxc.net.2.type = phys
2523 lxc.net.2.flags = up
2524 lxc.net.2.link = dummy0
2525 lxc.net.2.hwaddr = 4a:49:43:49:79:ff
2526 lxc.net.2.ipv4.address = 10.2.3.6/24
2527 lxc.net.2.ipv6.address = 2003:db8:1:0:214:1234:fe0b:3297
2528 lxc.cgroup.cpuset.cpus = 0,1
2529 lxc.cgroup.cpu.shares = 1234
2530 lxc.cgroup.devices.deny = a
2531 lxc.cgroup.devices.allow = c 1:3 rw
2532 lxc.cgroup.devices.allow = b 8:0 rw
2533 lxc.mount.fstab = /etc/fstab.complex
2534 lxc.mount.entry = /lib /root/myrootfs/lib none ro,bind 0 0
2535 lxc.rootfs.path = dir:/mnt/rootfs.complex
2536 lxc.cap.drop = sys_module mknod setuid net_raw
2537 lxc.cap.drop = mac_override
2538 </programlisting>
2539 </refsect2>
2540
2541 </refsect1>
2542
2543 <refsect1>
2544 <title>See Also</title>
2545 <simpara>
2546 <citerefentry>
2547 <refentrytitle><command>chroot</command></refentrytitle>
2548 <manvolnum>1</manvolnum>
2549 </citerefentry>,
2550
2551 <citerefentry>
2552 <refentrytitle><command>pivot_root</command></refentrytitle>
2553 <manvolnum>8</manvolnum>
2554 </citerefentry>,
2555
2556 <citerefentry>
2557 <refentrytitle><filename>fstab</filename></refentrytitle>
2558 <manvolnum>5</manvolnum>
2559 </citerefentry>,
2560
2561 <citerefentry>
2562 <refentrytitle><filename>capabilities</filename></refentrytitle>
2563 <manvolnum>7</manvolnum>
2564 </citerefentry>
2565 </simpara>
2566 </refsect1>
2567
2568 &seealso;
2569
2570 <refsect1>
2571 <title>Author</title>
2572 <para>Daniel Lezcano <email>daniel.lezcano@free.fr</email></para>
2573 </refsect1>
2574
2575 </refentry>
2576
2577 <!-- Keep this comment at the end of the file
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2580 sgml-omittag:t
2581 sgml-shorttag:t
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2583 sgml-always-quote-attributes:t
2584 sgml-indent-step:2
2585 sgml-indent-data:t
2586 sgml-parent-document:nil
2587 sgml-default-dtd-file:nil
2588 sgml-exposed-tags:nil
2589 sgml-local-catalogs:nil
2590 sgml-local-ecat-files:nil
2591 End:
2592 -->