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[pve-docs.git] / pct.adoc
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1ifdef::manvolnum[]
2PVE({manvolnum})
3================
38fd0958 4include::attributes.txt[]
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5
6NAME
7----
8
9pct - Tool to manage Linux Containers (LXC) on Proxmox VE
10
11
12SYNOPSYS
13--------
14
15include::pct.1-synopsis.adoc[]
16
17DESCRIPTION
18-----------
19endif::manvolnum[]
20
21ifndef::manvolnum[]
22Proxmox Container Toolkit
23=========================
38fd0958 24include::attributes.txt[]
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25endif::manvolnum[]
26
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27
28Containers are a lightweight alternative to fully virtualized
29VMs. Instead of emulating a complete Operating System (OS), containers
30simply use the OS of the host they run on. This implies that all
31containers use the same kernel, and that they can access resources
32from the host directly.
33
34This is great because containers do not waste CPU power nor memory due
35to kernel emulation. Container run-time costs are close to zero and
36usually negligible. But there are also some drawbacks you need to
37consider:
38
39* You can only run Linux based OS inside containers, i.e. it is not
a8e99754 40 possible to run FreeBSD or MS Windows inside.
4a2ae9ed 41
a8e99754 42* For security reasons, access to host resources needs to be
4a2ae9ed 43 restricted. This is done with AppArmor, SecComp filters and other
a8e99754 44 kernel features. Be prepared that some syscalls are not allowed
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45 inside containers.
46
47{pve} uses https://linuxcontainers.org/[LXC] as underlying container
48technology. We consider LXC as low-level library, which provides
a8e99754 49countless options. It would be too difficult to use those tools
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50directly. Instead, we provide a small wrapper called `pct`, the
51"Proxmox Container Toolkit".
52
a8e99754 53The toolkit is tightly coupled with {pve}. That means that it is aware
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54of the cluster setup, and it can use the same network and storage
55resources as fully virtualized VMs. You can even use the {pve}
56firewall, or manage containers using the HA framework.
57
58Our primary goal is to offer an environment as one would get from a
59VM, but without the additional overhead. We call this "System
60Containers".
61
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62NOTE: If you want to run micro-containers (with docker, rct, ...), it
63is best to run them inside a VM.
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64
65
66Security Considerations
67-----------------------
68
69Containers use the same kernel as the host, so there is a big attack
70surface for malicious users. You should consider this fact if you
71provide containers to totally untrusted people. In general, fully
a8e99754 72virtualized VMs provide better isolation.
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73
74The good news is that LXC uses many kernel security features like
75AppArmor, CGroups and PID and user namespaces, which makes containers
76usage quite secure. We distinguish two types of containers:
77
78Privileged containers
79~~~~~~~~~~~~~~~~~~~~~
80
81Security is done by dropping capabilities, using mandatory access
82control (AppArmor), SecComp filters and namespaces. The LXC team
83considers this kind of container as unsafe, and they will not consider
84new container escape exploits to be security issues worthy of a CVE
85and quick fix. So you should use this kind of containers only inside a
86trusted environment, or when no untrusted task is running as root in
87the container.
88
89Unprivileged containers
90~~~~~~~~~~~~~~~~~~~~~~~
91
a8e99754 92This kind of containers use a new kernel feature called user
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93namespaces. The root uid 0 inside the container is mapped to an
94unprivileged user outside the container. This means that most security
95issues (container escape, resource abuse, ...) in those containers
96will affect a random unprivileged user, and so would be a generic
a8e99754 97kernel security bug rather than an LXC issue. The LXC team thinks
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98unprivileged containers are safe by design.
99
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100
101Configuration
102-------------
103
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104The '/etc/pve/lxc/<CTID>.conf' file stores container configuration,
105where '<CTID>' is the numeric ID of the given container. Like all
106other files stored inside '/etc/pve/', they get automatically
107replicated to all other cluster nodes.
108
109NOTE: CTIDs < 100 are reserved for internal purposes, and CTIDs need to be
110unique cluster wide.
7fc230db 111
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112.Example Container Configuration
113----
114ostype: debian
115arch: amd64
116hostname: www
117memory: 512
118swap: 512
119net0: bridge=vmbr0,hwaddr=66:64:66:64:64:36,ip=dhcp,name=eth0,type=veth
120rootfs: local:107/vm-107-disk-1.raw,size=7G
121----
122
7fc230db 123Those configuration files are simple text files, and you can edit them
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124using a normal text editor ('vi', 'nano', ...). This is sometimes
125useful to do small corrections, but keep in mind that you need to
126restart the container to apply such changes.
127
128For that reason, it is usually better to use the 'pct' command to
129generate and modify those files, or do the whole thing using the GUI.
130Our toolkit is smart enough to instantaneously apply most changes to
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131running containers. This feature is called "hot plug", and there is no
132need to restart the container in that case.
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133
134File Format
135~~~~~~~~~~~
136
137Container configuration files use a simple colon separated key/value
138format. Each line has the following format:
139
140 # this is a comment
141 OPTION: value
142
143Blank lines in those files are ignored, and lines starting with a '#'
144character are treated as comments and are also ignored.
145
146It is possible to add low-level, LXC style configuration directly, for
147example:
148
149 lxc.init_cmd: /sbin/my_own_init
150
151or
152
153 lxc.init_cmd = /sbin/my_own_init
154
155Those settings are directly passed to the LXC low-level tools.
156
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157Snapshots
158~~~~~~~~~
159
160When you create a snapshot, 'pct' stores the configuration at snapshot
161time into a separate snapshot section within the same configuration
162file. For example, after creating a snapshot called 'testsnapshot',
163your configuration file will look like this:
164
165.Container Configuration with Snapshot
166----
167memory: 512
168swap: 512
169parent: testsnaphot
170...
171
172[testsnaphot]
173memory: 512
174swap: 512
175snaptime: 1457170803
176...
177----
178
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179There are a few snapshot related properties like 'parent' and
180'snaptime'. The 'parent' property is used to store the parent/child
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181relationship between snapshots. 'snaptime' is the snapshot creation
182time stamp (unix epoch).
7fc230db 183
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184Guest Operating System Configuration
185~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
186
187We normally try to detect the operating system type inside the
188container, and then modify some files inside the container to make
189them work as expected. Here is a short list of things we do at
190container startup:
191
192set /etc/hostname:: to set the container name
193
a8e99754 194modify /etc/hosts:: to allow lookup of the local hostname
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195
196network setup:: pass the complete network setup to the container
197
198configure DNS:: pass information about DNS servers
199
a8e99754 200adapt the init system:: for example, fix the number of spawned getty processes
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201
202set the root password:: when creating a new container
203
204rewrite ssh_host_keys:: so that each container has unique keys
205
a8e99754 206randomize crontab:: so that cron does not start at the same time on all containers
3f13c1c3 207
a8e99754 208The above task depends on the OS type, so the implementation is different
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209for each OS type. You can also disable any modifications by manually
210setting the 'ostype' to 'unmanaged'.
211
212OS type detection is done by testing for certain files inside the
213container:
214
215Ubuntu:: inspect /etc/lsb-release ('DISTRIB_ID=Ubuntu')
216
217Debian:: test /etc/debian_version
218
219Fedora:: test /etc/fedora-release
220
221RedHat or CentOS:: test /etc/redhat-release
222
223ArchLinux:: test /etc/arch-release
224
225Alpine:: test /etc/alpine-release
226
a8e99754 227NOTE: Container start fails if the configured 'ostype' differs from the auto
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228detected type.
229
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230
231Container Images
232----------------
233
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234Container Images, sometimes also referred to as "templates" or
235"appliances", are 'tar' archives which contain everything to run a
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236container. You can think of it as a tidy container backup. Like most
237modern container toolkits, 'pct' uses those images when you create a
238new container, for example:
239
240 pct create 999 local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz
241
242Proxmox itself ships a set of basic templates for most common
243operating systems, and you can download them using the 'pveam' (short
244for {pve} Appliance Manager) command line utility. You can also
245download https://www.turnkeylinux.org/[TurnKey Linux] containers using
246that tool (or the graphical user interface).
247
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248Our image repositories contain a list of available images, and there
249is a cron job run each day to download that list. You can trigger that
250update manually with:
251
252 pveam update
253
254After that you can view the list of available images using:
255
256 pveam available
257
258You can restrict this large list by specifying the 'section' you are
259interested in, for example basic 'system' images:
260
261.List available system images
262----
263# pveam available --section system
264system archlinux-base_2015-24-29-1_x86_64.tar.gz
265system centos-7-default_20160205_amd64.tar.xz
266system debian-6.0-standard_6.0-7_amd64.tar.gz
267system debian-7.0-standard_7.0-3_amd64.tar.gz
268system debian-8.0-standard_8.0-1_amd64.tar.gz
269system ubuntu-12.04-standard_12.04-1_amd64.tar.gz
270system ubuntu-14.04-standard_14.04-1_amd64.tar.gz
271system ubuntu-15.04-standard_15.04-1_amd64.tar.gz
272system ubuntu-15.10-standard_15.10-1_amd64.tar.gz
273----
274
a8e99754 275Before you can use such a template, you need to download them into one
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276of your storages. You can simply use storage 'local' for that
277purpose. For clustered installations, it is preferred to use a shared
278storage so that all nodes can access those images.
279
280 pveam download local debian-8.0-standard_8.0-1_amd64.tar.gz
281
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282You are now ready to create containers using that image, and you can
283list all downloaded images on storage 'local' with:
284
285----
286# pveam list local
287local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz 190.20MB
288----
289
a8e99754 290The above command shows you the full {pve} volume identifiers. They include
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291the storage name, and most other {pve} commands can use them. For
292examply you can delete that image later with:
293
294 pveam remove local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz
3a6fa247 295
d61bab51 296
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297Container Storage
298-----------------
299
300Traditional containers use a very simple storage model, only allowing
301a single mount point, the root file system. This was further
302restricted to specific file system types like 'ext4' and 'nfs'.
303Additional mounts are often done by user provided scripts. This turend
a8e99754 304out to be complex and error prone, so we try to avoid that now.
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305
306Our new LXC based container model is more flexible regarding
307storage. First, you can have more than a single mount point. This
308allows you to choose a suitable storage for each application. For
309example, you can use a relatively slow (and thus cheap) storage for
310the container root file system. Then you can use a second mount point
311to mount a very fast, distributed storage for your database
312application.
313
314The second big improvement is that you can use any storage type
315supported by the {pve} storage library. That means that you can store
316your containers on local 'lvmthin' or 'zfs', shared 'iSCSI' storage,
a8e99754 317or even on distributed storage systems like 'ceph'. It also enables us
70a42028 318to use advanced storage features like snapshots and clones. 'vzdump'
a8e99754 319can also use the snapshot feature to provide consistent container
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320backups.
321
322Last but not least, you can also mount local devices directly, or
323mount local directories using bind mounts. That way you can access
324local storage inside containers with zero overhead. Such bind mounts
a8e99754 325also provide an easy way to share data between different containers.
70a42028 326
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327
328Managing Containers with 'pct'
329------------------------------
330
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331'pct' is the tool to manage Linux Containers on {pve}. You can create
332and destroy containers, and control execution (start, stop, migrate,
333...). You can use pct to set parameters in the associated config file,
a8e99754 334like network configuration or memory limits.
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335
336CLI Usage Examples
337------------------
338
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339Create a container based on a Debian template (provided you have
340already downloaded the template via the webgui)
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341
342 pct create 100 /var/lib/vz/template/cache/debian-8.0-standard_8.0-1_amd64.tar.gz
343
344Start container 100
345
346 pct start 100
347
348Start a login session via getty
349
350 pct console 100
351
352Enter the LXC namespace and run a shell as root user
353
354 pct enter 100
355
356Display the configuration
357
358 pct config 100
359
360Add a network interface called eth0, bridged to the host bridge vmbr0,
361set the address and gateway, while it's running
362
363 pct set 100 -net0 name=eth0,bridge=vmbr0,ip=192.168.15.147/24,gw=192.168.15.1
364
365Reduce the memory of the container to 512MB
366
367 pct set -memory 512 100
368
369Files
370------
371
9dfe82f1 372'/etc/pve/lxc/<CTID>.conf'::
0c6b782f 373
9dfe82f1 374Configuration file for the container '<CTID>'.
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375
376
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377Container Mountpoints
378---------------------
379
380Beside the root directory the container can also have additional mountpoints.
381Currently there are basically three types of mountpoints: storage backed
382mountpoints, bind mounts and device mounts.
383
384Storage backed mountpoints are managed by the {pve} storage subsystem and come
385in three different flavors:
386
387- Image based: These are raw images containing a single ext4 formatted file
388 system.
389- ZFS Subvolumes: These are technically bind mounts, but with managed storage,
390 and thus allow resizing and snapshotting.
391- Directories: passing `size=0` triggers a special case where instead of a raw
392 image a directory is created.
393
394Bind mounts are considered to not be managed by the storage subsystem, so you
395cannot make snapshots or deal with quotas from inside the container, and with
396unprivileged containers you might run into permission problems caused by the
397user mapping, and cannot use ACLs from inside an unprivileged container.
398
399Similarly device mounts are not managed by the storage, but for these the
400`quota` and `acl` options will be honored.
401
402
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403Using quotas inside containers
404------------------------------
405
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406Quotas allow to set limits inside a container for the amount of disk space
407that each user can use.
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408This only works on ext4 image based storage types and currently does not work
409with unprivileged containers.
410
411Activating the `quota` option causes the following mount options to be used for
412a mountpoint: `usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0`
413
414This allows quotas to be used like you would on any other system. You can
415initialize the `/aquota.user` and `/aquota.group` files by running
416
417 quotacheck -cmug /
418 quotaon /
419
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420and edit the quotas via the `edquota` command. Refer to the documentation
421of the distribution running inside the container for details.
422
423NOTE: You need to run the above commands for every mountpoint by passing
424the mountpoint's path instead of just `/`.
d6ed3622 425
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426Using ACLs inside containers
427----------------------------
428
429The standard Posix Access Control Lists are also available inside containers.
430ACLs allow you to set more detailed file ownership than the traditional user/
431group/others model.
d6ed3622 432
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433Container Advantages
434--------------------
435
436- Simple, and fully integrated into {pve}. Setup looks similar to a normal
437 VM setup.
438
439 * Storage (ZFS, LVM, NFS, Ceph, ...)
440
441 * Network
442
443 * Authentification
444
445 * Cluster
446
447- Fast: minimal overhead, as fast as bare metal
448
449- High density (perfect for idle workloads)
450
451- REST API
452
453- Direct hardware access
454
455
456Technology Overview
457-------------------
458
459- Integrated into {pve} graphical user interface (GUI)
460
461- LXC (https://linuxcontainers.org/)
462
463- cgmanager for cgroup management
464
465- lxcfs to provive containerized /proc file system
466
467- apparmor
468
469- CRIU: for live migration (planned)
470
471- We use latest available kernels (4.2.X)
472
a8e99754 473- Image based deployment (templates)
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474
475- Container setup from host (Network, DNS, Storage, ...)
476
477
478ifdef::manvolnum[]
479include::pve-copyright.adoc[]
480endif::manvolnum[]
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