4 include::attributes.txt[]
11 pct - Tool to manage Linux Containers (LXC) on Proxmox VE
17 include::pct.1-synopsis.adoc[]
24 Proxmox Container Toolkit
25 =========================
26 include::attributes.txt[]
33 Containers are a lightweight alternative to fully virtualized
34 VMs. Instead of emulating a complete Operating System (OS), containers
35 simply use the OS of the host they run on. This implies that all
36 containers use the same kernel, and that they can access resources
37 from the host directly.
39 This is great because containers do not waste CPU power nor memory due
40 to kernel emulation. Container run-time costs are close to zero and
41 usually negligible. But there are also some drawbacks you need to
44 * You can only run Linux based OS inside containers, i.e. it is not
45 possible to run FreeBSD or MS Windows inside.
47 * For security reasons, access to host resources needs to be
48 restricted. This is done with AppArmor, SecComp filters and other
49 kernel features. Be prepared that some syscalls are not allowed
52 {pve} uses https://linuxcontainers.org/[LXC] as underlying container
53 technology. We consider LXC as low-level library, which provides
54 countless options. It would be too difficult to use those tools
55 directly. Instead, we provide a small wrapper called `pct`, the
56 "Proxmox Container Toolkit".
58 The toolkit is tightly coupled with {pve}. That means that it is aware
59 of the cluster setup, and it can use the same network and storage
60 resources as fully virtualized VMs. You can even use the {pve}
61 firewall, or manage containers using the HA framework.
63 Our primary goal is to offer an environment as one would get from a
64 VM, but without the additional overhead. We call this "System
67 NOTE: If you want to run micro-containers (with docker, rkt, ...), it
68 is best to run them inside a VM.
71 Security Considerations
72 -----------------------
74 Containers use the same kernel as the host, so there is a big attack
75 surface for malicious users. You should consider this fact if you
76 provide containers to totally untrusted people. In general, fully
77 virtualized VMs provide better isolation.
79 The good news is that LXC uses many kernel security features like
80 AppArmor, CGroups and PID and user namespaces, which makes containers
81 usage quite secure. We distinguish two types of containers:
87 Security is done by dropping capabilities, using mandatory access
88 control (AppArmor), SecComp filters and namespaces. The LXC team
89 considers this kind of container as unsafe, and they will not consider
90 new container escape exploits to be security issues worthy of a CVE
91 and quick fix. So you should use this kind of containers only inside a
92 trusted environment, or when no untrusted task is running as root in
96 Unprivileged Containers
97 ~~~~~~~~~~~~~~~~~~~~~~~
99 This kind of containers use a new kernel feature called user
100 namespaces. The root UID 0 inside the container is mapped to an
101 unprivileged user outside the container. This means that most security
102 issues (container escape, resource abuse, ...) in those containers
103 will affect a random unprivileged user, and so would be a generic
104 kernel security bug rather than an LXC issue. The LXC team thinks
105 unprivileged containers are safe by design.
111 The `/etc/pve/lxc/<CTID>.conf` file stores container configuration,
112 where `<CTID>` is the numeric ID of the given container. Like all
113 other files stored inside `/etc/pve/`, they get automatically
114 replicated to all other cluster nodes.
116 NOTE: CTIDs < 100 are reserved for internal purposes, and CTIDs need to be
119 .Example Container Configuration
126 net0: bridge=vmbr0,hwaddr=66:64:66:64:64:36,ip=dhcp,name=eth0,type=veth
127 rootfs: local:107/vm-107-disk-1.raw,size=7G
130 Those configuration files are simple text files, and you can edit them
131 using a normal text editor (`vi`, `nano`, ...). This is sometimes
132 useful to do small corrections, but keep in mind that you need to
133 restart the container to apply such changes.
135 For that reason, it is usually better to use the `pct` command to
136 generate and modify those files, or do the whole thing using the GUI.
137 Our toolkit is smart enough to instantaneously apply most changes to
138 running containers. This feature is called "hot plug", and there is no
139 need to restart the container in that case.
145 Container configuration files use a simple colon separated key/value
146 format. Each line has the following format:
153 Blank lines in those files are ignored, and lines starting with a `#`
154 character are treated as comments and are also ignored.
156 It is possible to add low-level, LXC style configuration directly, for
159 lxc.init_cmd: /sbin/my_own_init
163 lxc.init_cmd = /sbin/my_own_init
165 Those settings are directly passed to the LXC low-level tools.
171 When you create a snapshot, `pct` stores the configuration at snapshot
172 time into a separate snapshot section within the same configuration
173 file. For example, after creating a snapshot called ``testsnapshot'',
174 your configuration file will look like this:
176 .Container configuration with snapshot
190 There are a few snapshot related properties like `parent` and
191 `snaptime`. The `parent` property is used to store the parent/child
192 relationship between snapshots. `snaptime` is the snapshot creation
193 time stamp (Unix epoch).
196 Guest Operating System Configuration
197 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
199 We normally try to detect the operating system type inside the
200 container, and then modify some files inside the container to make
201 them work as expected. Here is a short list of things we do at
204 set /etc/hostname:: to set the container name
206 modify /etc/hosts:: to allow lookup of the local hostname
208 network setup:: pass the complete network setup to the container
210 configure DNS:: pass information about DNS servers
212 adapt the init system:: for example, fix the number of spawned getty processes
214 set the root password:: when creating a new container
216 rewrite ssh_host_keys:: so that each container has unique keys
218 randomize crontab:: so that cron does not start at the same time on all containers
220 Changes made by {PVE} are enclosed by comment markers:
228 Those markers will be inserted at a reasonable location in the
229 file. If such a section already exists, it will be updated in place
230 and will not be moved.
232 Modification of a file can be prevented by adding a `.pve-ignore.`
233 file for it. For instance, if the file `/etc/.pve-ignore.hosts`
234 exists then the `/etc/hosts` file will not be touched. This can be a
235 simple empty file creatd via:
237 # touch /etc/.pve-ignore.hosts
239 Most modifications are OS dependent, so they differ between different
240 distributions and versions. You can completely disable modifications
241 by manually setting the `ostype` to `unmanaged`.
243 OS type detection is done by testing for certain files inside the
246 Ubuntu:: inspect /etc/lsb-release (`DISTRIB_ID=Ubuntu`)
248 Debian:: test /etc/debian_version
250 Fedora:: test /etc/fedora-release
252 RedHat or CentOS:: test /etc/redhat-release
254 ArchLinux:: test /etc/arch-release
256 Alpine:: test /etc/alpine-release
258 Gentoo:: test /etc/gentoo-release
260 NOTE: Container start fails if the configured `ostype` differs from the auto
267 include::pct.conf.5-opts.adoc[]
273 Container images, sometimes also referred to as ``templates'' or
274 ``appliances'', are `tar` archives which contain everything to run a
275 container. You can think of it as a tidy container backup. Like most
276 modern container toolkits, `pct` uses those images when you create a
277 new container, for example:
279 pct create 999 local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz
281 {pve} itself ships a set of basic templates for most common
282 operating systems, and you can download them using the `pveam` (short
283 for {pve} Appliance Manager) command line utility. You can also
284 download https://www.turnkeylinux.org/[TurnKey Linux] containers using
285 that tool (or the graphical user interface).
287 Our image repositories contain a list of available images, and there
288 is a cron job run each day to download that list. You can trigger that
289 update manually with:
293 After that you can view the list of available images using:
297 You can restrict this large list by specifying the `section` you are
298 interested in, for example basic `system` images:
300 .List available system images
302 # pveam available --section system
303 system archlinux-base_2015-24-29-1_x86_64.tar.gz
304 system centos-7-default_20160205_amd64.tar.xz
305 system debian-6.0-standard_6.0-7_amd64.tar.gz
306 system debian-7.0-standard_7.0-3_amd64.tar.gz
307 system debian-8.0-standard_8.0-1_amd64.tar.gz
308 system ubuntu-12.04-standard_12.04-1_amd64.tar.gz
309 system ubuntu-14.04-standard_14.04-1_amd64.tar.gz
310 system ubuntu-15.04-standard_15.04-1_amd64.tar.gz
311 system ubuntu-15.10-standard_15.10-1_amd64.tar.gz
314 Before you can use such a template, you need to download them into one
315 of your storages. You can simply use storage `local` for that
316 purpose. For clustered installations, it is preferred to use a shared
317 storage so that all nodes can access those images.
319 pveam download local debian-8.0-standard_8.0-1_amd64.tar.gz
321 You are now ready to create containers using that image, and you can
322 list all downloaded images on storage `local` with:
326 local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz 190.20MB
329 The above command shows you the full {pve} volume identifiers. They include
330 the storage name, and most other {pve} commands can use them. For
331 example you can delete that image later with:
333 pveam remove local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz
339 Traditional containers use a very simple storage model, only allowing
340 a single mount point, the root file system. This was further
341 restricted to specific file system types like `ext4` and `nfs`.
342 Additional mounts are often done by user provided scripts. This turned
343 out to be complex and error prone, so we try to avoid that now.
345 Our new LXC based container model is more flexible regarding
346 storage. First, you can have more than a single mount point. This
347 allows you to choose a suitable storage for each application. For
348 example, you can use a relatively slow (and thus cheap) storage for
349 the container root file system. Then you can use a second mount point
350 to mount a very fast, distributed storage for your database
353 The second big improvement is that you can use any storage type
354 supported by the {pve} storage library. That means that you can store
355 your containers on local `lvmthin` or `zfs`, shared `iSCSI` storage,
356 or even on distributed storage systems like `ceph`. It also enables us
357 to use advanced storage features like snapshots and clones. `vzdump`
358 can also use the snapshot feature to provide consistent container
361 Last but not least, you can also mount local devices directly, or
362 mount local directories using bind mounts. That way you can access
363 local storage inside containers with zero overhead. Such bind mounts
364 also provide an easy way to share data between different containers.
370 The root mount point is configured with the `rootfs` property, and you can
371 configure up to 10 additional mount points. The corresponding options
372 are called `mp0` to `mp9`, and they can contain the following setting:
374 include::pct-mountpoint-opts.adoc[]
376 Currently there are basically three types of mount points: storage backed
377 mount points, bind mounts and device mounts.
379 .Typical container `rootfs` configuration
381 rootfs: thin1:base-100-disk-1,size=8G
385 Storage Backed Mount Points
386 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
388 Storage backed mount points are managed by the {pve} storage subsystem and come
389 in three different flavors:
391 - Image based: these are raw images containing a single ext4 formatted file
393 - ZFS subvolumes: these are technically bind mounts, but with managed storage,
394 and thus allow resizing and snapshotting.
395 - Directories: passing `size=0` triggers a special case where instead of a raw
396 image a directory is created.
402 Bind mounts allow you to access arbitrary directories from your Proxmox VE host
403 inside a container. Some potential use cases are:
405 - Accessing your home directory in the guest
406 - Accessing an USB device directory in the guest
407 - Accessing an NFS mount from the host in the guest
409 Bind mounts are considered to not be managed by the storage subsystem, so you
410 cannot make snapshots or deal with quotas from inside the container. With
411 unprivileged containers you might run into permission problems caused by the
412 user mapping and cannot use ACLs.
414 NOTE: The contents of bind mount points are not backed up when using `vzdump`.
416 WARNING: For security reasons, bind mounts should only be established
417 using source directories especially reserved for this purpose, e.g., a
418 directory hierarchy under `/mnt/bindmounts`. Never bind mount system
419 directories like `/`, `/var` or `/etc` into a container - this poses a
422 NOTE: The bind mount source path must not contain any symlinks.
424 For example, to make the directory `/mnt/bindmounts/shared` accessible in the
425 container with ID `100` under the path `/shared`, use a configuration line like
426 `mp0: /mnt/bindmounts/shared,mp=/shared` in `/etc/pve/lxc/100.conf`.
427 Alternatively, use `pct set 100 -mp0 /mnt/bindmounts/shared,mp=/shared` to
428 achieve the same result.
434 Device mount points allow to mount block devices of the host directly into the
435 container. Similar to bind mounts, device mounts are not managed by {PVE}'s
436 storage subsystem, but the `quota` and `acl` options will be honored.
438 NOTE: Device mount points should only be used under special circumstances. In
439 most cases a storage backed mount point offers the same performance and a lot
442 NOTE: The contents of device mount points are not backed up when using `vzdump`.
448 WARNING: Because of existing issues in the Linux kernel's freezer
449 subsystem the usage of FUSE mounts inside a container is strongly
450 advised against, as containers need to be frozen for suspend or
451 snapshot mode backups.
453 If FUSE mounts cannot be replaced by other mounting mechanisms or storage
454 technologies, it is possible to establish the FUSE mount on the Proxmox host
455 and use a bind mount point to make it accessible inside the container.
458 Using Quotas Inside Containers
459 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
461 Quotas allow to set limits inside a container for the amount of disk
462 space that each user can use. This only works on ext4 image based
463 storage types and currently does not work with unprivileged
466 Activating the `quota` option causes the following mount options to be
467 used for a mount point:
468 `usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0`
470 This allows quotas to be used like you would on any other system. You
471 can initialize the `/aquota.user` and `/aquota.group` files by running
478 and edit the quotas via the `edquota` command. Refer to the documentation
479 of the distribution running inside the container for details.
481 NOTE: You need to run the above commands for every mount point by passing
482 the mount point's path instead of just `/`.
485 Using ACLs Inside Containers
486 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
488 The standard Posix **A**ccess **C**ontrol **L**ists are also available inside containers.
489 ACLs allow you to set more detailed file ownership than the traditional user/
496 You can configure up to 10 network interfaces for a single
497 container. The corresponding options are called `net0` to `net9`, and
498 they can contain the following setting:
500 include::pct-network-opts.adoc[]
510 It is possible to use the `vzdump` tool for container backup. Please
511 refer to the `vzdump` manual page for details.
514 Restoring Container Backups
515 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
517 Restoring container backups made with `vzdump` is possible using the
518 `pct restore` command. By default, `pct restore` will attempt to restore as much
519 of the backed up container configuration as possible. It is possible to override
520 the backed up configuration by manually setting container options on the command
521 line (see the `pct` manual page for details).
523 NOTE: `pvesm extractconfig` can be used to view the backed up configuration
524 contained in a vzdump archive.
526 There are two basic restore modes, only differing by their handling of mount
530 ``Simple'' Restore Mode
531 ^^^^^^^^^^^^^^^^^^^^^^^
533 If neither the `rootfs` parameter nor any of the optional `mpX` parameters
534 are explicitly set, the mount point configuration from the backed up
535 configuration file is restored using the following steps:
537 . Extract mount points and their options from backup
538 . Create volumes for storage backed mount points (on storage provided with the
539 `storage` parameter, or default local storage if unset)
540 . Extract files from backup archive
541 . Add bind and device mount points to restored configuration (limited to root user)
543 NOTE: Since bind and device mount points are never backed up, no files are
544 restored in the last step, but only the configuration options. The assumption
545 is that such mount points are either backed up with another mechanism (e.g.,
546 NFS space that is bind mounted into many containers), or not intended to be
549 This simple mode is also used by the container restore operations in the web
553 ``Advanced'' Restore Mode
554 ^^^^^^^^^^^^^^^^^^^^^^^^^
556 By setting the `rootfs` parameter (and optionally, any combination of `mpX`
557 parameters), the `pct restore` command is automatically switched into an
558 advanced mode. This advanced mode completely ignores the `rootfs` and `mpX`
559 configuration options contained in the backup archive, and instead only
560 uses the options explicitly provided as parameters.
562 This mode allows flexible configuration of mount point settings at restore time,
565 * Set target storages, volume sizes and other options for each mount point
567 * Redistribute backed up files according to new mount point scheme
568 * Restore to device and/or bind mount points (limited to root user)
571 Managing Containers with `pct`
572 ------------------------------
574 `pct` is the tool to manage Linux Containers on {pve}. You can create
575 and destroy containers, and control execution (start, stop, migrate,
576 ...). You can use pct to set parameters in the associated config file,
577 like network configuration or memory limits.
583 Create a container based on a Debian template (provided you have
584 already downloaded the template via the web interface)
586 pct create 100 /var/lib/vz/template/cache/debian-8.0-standard_8.0-1_amd64.tar.gz
592 Start a login session via getty
596 Enter the LXC namespace and run a shell as root user
600 Display the configuration
604 Add a network interface called `eth0`, bridged to the host bridge `vmbr0`,
605 set the address and gateway, while it's running
607 pct set 100 -net0 name=eth0,bridge=vmbr0,ip=192.168.15.147/24,gw=192.168.15.1
609 Reduce the memory of the container to 512MB
611 pct set 100 -memory 512
614 Obtaining Debugging Logs
615 ~~~~~~~~~~~~~~~~~~~~~~~~
617 In case `pct start` is unable to start a specific container, it might be
618 helpful to collect debugging output by running `lxc-start` (replace `ID` with
621 lxc-start -n ID -F -l DEBUG -o /tmp/lxc-ID.log
623 This command will attempt to start the container in foreground mode, to stop the container run `pct shutdown ID` or `pct stop ID` in a second terminal.
625 The collected debug log is written to `/tmp/lxc-ID.log`.
627 NOTE: If you have changed the container's configuration since the last start
628 attempt with `pct start`, you need to run `pct start` at least once to also
629 update the configuration used by `lxc-start`.
635 `/etc/pve/lxc/<CTID>.conf`::
637 Configuration file for the container '<CTID>'.
643 * Simple, and fully integrated into {pve}. Setup looks similar to a normal
646 ** Storage (ZFS, LVM, NFS, Ceph, ...)
654 * Fast: minimal overhead, as fast as bare metal
656 * High density (perfect for idle workloads)
660 * Direct hardware access
666 * Integrated into {pve} graphical user interface (GUI)
668 * LXC (https://linuxcontainers.org/)
670 * lxcfs to provide containerized /proc file system
674 * CRIU: for live migration (planned)
676 * We use latest available kernels (4.4.X)
678 * Image based deployment (templates)
680 * Container setup from host (network, DNS, storage, ...)
684 include::pve-copyright.adoc[]