10 pct - Tool to manage Linux Containers (LXC) on Proxmox VE
16 include::pct.1-synopsis.adoc[]
23 Proxmox Container Toolkit
24 =========================
28 :title: Linux Container
31 Containers are a lightweight alternative to fully virtualized machines (VMs).
32 They use the kernel of the host system that they run on, instead of emulating a
33 full operating system (OS). This means that containers can access resources on
34 the host system directly.
36 The runtime costs for containers is low, usually negligible. However, there are
37 some drawbacks that need be considered:
39 * Only Linux distributions can be run in containers. It is not possible to run
40 other Operating Systems like, for example, FreeBSD or Microsoft Windows
43 * For security reasons, access to host resources needs to be restricted.
44 Containers run in their own separate namespaces. Additionally some syscalls
45 are not allowed within containers.
47 {pve} uses https://linuxcontainers.org/[Linux Containers (LXC)] as underlying
48 container technology. The ``Proxmox Container Toolkit'' (`pct`) simplifies the
49 usage and management of LXC containers.
51 Containers are tightly integrated with {pve}. This means that they are aware of
52 the cluster setup, and they can use the same network and storage resources as
53 virtual machines. You can also use the {pve} firewall, or manage containers
54 using the HA framework.
56 Our primary goal is to offer an environment as one would get from a VM, but
57 without the additional overhead. We call this ``System Containers''.
59 NOTE: If you want to run micro-containers, for example, 'Docker' or 'rkt', it
60 is best to run them inside a VM.
66 * LXC (https://linuxcontainers.org/)
68 * Integrated into {pve} graphical web user interface (GUI)
70 * Easy to use command line tool `pct`
72 * Access via {pve} REST API
74 * 'lxcfs' to provide containerized /proc file system
76 * Control groups ('cgroups') for resource isolation and limitation
78 * 'AppArmor' and 'seccomp' to improve security
80 * Modern Linux kernels
82 * Image based deployment (templates)
84 * Uses {pve} xref:chapter_storage[storage library]
86 * Container setup from host (network, DNS, storage, etc.)
89 [[pct_container_images]]
93 Container images, sometimes also referred to as ``templates'' or
94 ``appliances'', are `tar` archives which contain everything to run a container.
96 {pve} itself provides a variety of basic templates for the most common Linux
97 distributions. They can be downloaded using the GUI or the `pveam` (short for
98 {pve} Appliance Manager) command line utility.
99 Additionally, https://www.turnkeylinux.org/[TurnKey Linux] container templates
100 are also available to download.
102 The list of available templates is updated daily through the 'pve-daily-update'
103 timer. You can also trigger an update manually by executing:
109 To view the list of available images run:
115 You can restrict this large list by specifying the `section` you are
116 interested in, for example basic `system` images:
118 .List available system images
120 # pveam available --section system
121 system alpine-3.10-default_20190626_amd64.tar.xz
122 system alpine-3.9-default_20190224_amd64.tar.xz
123 system archlinux-base_20190924-1_amd64.tar.gz
124 system centos-6-default_20191016_amd64.tar.xz
125 system centos-7-default_20190926_amd64.tar.xz
126 system centos-8-default_20191016_amd64.tar.xz
127 system debian-10.0-standard_10.0-1_amd64.tar.gz
128 system debian-8.0-standard_8.11-1_amd64.tar.gz
129 system debian-9.0-standard_9.7-1_amd64.tar.gz
130 system fedora-30-default_20190718_amd64.tar.xz
131 system fedora-31-default_20191029_amd64.tar.xz
132 system gentoo-current-default_20190718_amd64.tar.xz
133 system opensuse-15.0-default_20180907_amd64.tar.xz
134 system opensuse-15.1-default_20190719_amd64.tar.xz
135 system ubuntu-16.04-standard_16.04.5-1_amd64.tar.gz
136 system ubuntu-18.04-standard_18.04.1-1_amd64.tar.gz
137 system ubuntu-19.04-standard_19.04-1_amd64.tar.gz
138 system ubuntu-19.10-standard_19.10-1_amd64.tar.gz
141 Before you can use such a template, you need to download them into one of your
142 storages. If you're unsure to which one, you can simply use the `local` named
143 storage for that purpose. For clustered installations, it is preferred to use a
144 shared storage so that all nodes can access those images.
147 # pveam download local debian-10.0-standard_10.0-1_amd64.tar.gz
150 You are now ready to create containers using that image, and you can list all
151 downloaded images on storage `local` with:
155 local:vztmpl/debian-10.0-standard_10.0-1_amd64.tar.gz 219.95MB
158 TIP: You can also use the {pve} web interface GUI to download, list and delete
161 `pct` uses them to create a new container, for example:
164 # pct create 999 local:vztmpl/debian-10.0-standard_10.0-1_amd64.tar.gz
167 The above command shows you the full {pve} volume identifiers. They include the
168 storage name, and most other {pve} commands can use them. For example you can
169 delete that image later with:
172 # pveam remove local:vztmpl/debian-10.0-standard_10.0-1_amd64.tar.gz
184 [thumbnail="screenshot/gui-create-ct-general.png"]
186 General settings of a container include
188 * the *Node* : the physical server on which the container will run
189 * the *CT ID*: a unique number in this {pve} installation used to identify your
191 * *Hostname*: the hostname of the container
192 * *Resource Pool*: a logical group of containers and VMs
193 * *Password*: the root password of the container
194 * *SSH Public Key*: a public key for connecting to the root account over SSH
195 * *Unprivileged container*: this option allows to choose at creation time
196 if you want to create a privileged or unprivileged container.
198 Unprivileged Containers
199 ^^^^^^^^^^^^^^^^^^^^^^^
201 Unprivileged containers use a new kernel feature called user namespaces.
202 The root UID 0 inside the container is mapped to an unprivileged user outside
203 the container. This means that most security issues (container escape, resource
204 abuse, etc.) in these containers will affect a random unprivileged user, and
205 would be a generic kernel security bug rather than an LXC issue. The LXC team
206 thinks unprivileged containers are safe by design.
208 This is the default option when creating a new container.
210 NOTE: If the container uses systemd as an init system, please be aware the
211 systemd version running inside the container should be equal to or greater than
215 Privileged Containers
216 ^^^^^^^^^^^^^^^^^^^^^
218 Security in containers is achieved by using mandatory access control 'AppArmor'
219 restrictions, 'seccomp' filters and Linux kernel namespaces. The LXC team
220 considers this kind of container as unsafe, and they will not consider new
221 container escape exploits to be security issues worthy of a CVE and quick fix.
222 That's why privileged containers should only be used in trusted environments.
229 [thumbnail="screenshot/gui-create-ct-cpu.png"]
231 You can restrict the number of visible CPUs inside the container using the
232 `cores` option. This is implemented using the Linux 'cpuset' cgroup
233 (**c**ontrol *group*).
234 A special task inside `pvestatd` tries to distribute running containers among
235 available CPUs periodically.
236 To view the assigned CPUs run the following command:
240 ---------------------
244 ---------------------
247 Containers use the host kernel directly. All tasks inside a container are
248 handled by the host CPU scheduler. {pve} uses the Linux 'CFS' (**C**ompletely
249 **F**air **S**cheduler) scheduler by default, which has additional bandwidth
254 `cpulimit`: :: You can use this option to further limit assigned CPU time.
255 Please note that this is a floating point number, so it is perfectly valid to
256 assign two cores to a container, but restrict overall CPU consumption to half a
264 `cpuunits`: :: This is a relative weight passed to the kernel scheduler. The
265 larger the number is, the more CPU time this container gets. Number is relative
266 to the weights of all the other running containers. The default is 1024. You
267 can use this setting to prioritize some containers.
274 [thumbnail="screenshot/gui-create-ct-memory.png"]
276 Container memory is controlled using the cgroup memory controller.
280 `memory`: :: Limit overall memory usage. This corresponds to the
281 `memory.limit_in_bytes` cgroup setting.
283 `swap`: :: Allows the container to use additional swap memory from the host
284 swap space. This corresponds to the `memory.memsw.limit_in_bytes` cgroup
285 setting, which is set to the sum of both value (`memory + swap`).
292 [thumbnail="screenshot/gui-create-ct-root-disk.png"]
294 The root mount point is configured with the `rootfs` property. You can
295 configure up to 256 additional mount points. The corresponding options are
296 called `mp0` to `mp255`. They can contain the following settings:
298 include::pct-mountpoint-opts.adoc[]
300 Currently there are three types of mount points: storage backed mount points,
301 bind mounts, and device mounts.
303 .Typical container `rootfs` configuration
305 rootfs: thin1:base-100-disk-1,size=8G
309 Storage Backed Mount Points
310 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
312 Storage backed mount points are managed by the {pve} storage subsystem and come
313 in three different flavors:
315 - Image based: these are raw images containing a single ext4 formatted file
317 - ZFS subvolumes: these are technically bind mounts, but with managed storage,
318 and thus allow resizing and snapshotting.
319 - Directories: passing `size=0` triggers a special case where instead of a raw
320 image a directory is created.
322 NOTE: The special option syntax `STORAGE_ID:SIZE_IN_GB` for storage backed
323 mount point volumes will automatically allocate a volume of the specified size
324 on the specified storage. For example, calling
327 pct set 100 -mp0 thin1:10,mp=/path/in/container
330 will allocate a 10GB volume on the storage `thin1` and replace the volume ID
331 place holder `10` with the allocated volume ID, and setup the moutpoint in the
332 container at `/path/in/container`
338 Bind mounts allow you to access arbitrary directories from your Proxmox VE host
339 inside a container. Some potential use cases are:
341 - Accessing your home directory in the guest
342 - Accessing an USB device directory in the guest
343 - Accessing an NFS mount from the host in the guest
345 Bind mounts are considered to not be managed by the storage subsystem, so you
346 cannot make snapshots or deal with quotas from inside the container. With
347 unprivileged containers you might run into permission problems caused by the
348 user mapping and cannot use ACLs.
350 NOTE: The contents of bind mount points are not backed up when using `vzdump`.
352 WARNING: For security reasons, bind mounts should only be established using
353 source directories especially reserved for this purpose, e.g., a directory
354 hierarchy under `/mnt/bindmounts`. Never bind mount system directories like
355 `/`, `/var` or `/etc` into a container - this poses a great security risk.
357 NOTE: The bind mount source path must not contain any symlinks.
359 For example, to make the directory `/mnt/bindmounts/shared` accessible in the
360 container with ID `100` under the path `/shared`, use a configuration line like
361 `mp0: /mnt/bindmounts/shared,mp=/shared` in `/etc/pve/lxc/100.conf`.
362 Alternatively, use `pct set 100 -mp0 /mnt/bindmounts/shared,mp=/shared` to
363 achieve the same result.
369 Device mount points allow to mount block devices of the host directly into the
370 container. Similar to bind mounts, device mounts are not managed by {PVE}'s
371 storage subsystem, but the `quota` and `acl` options will be honored.
373 NOTE: Device mount points should only be used under special circumstances. In
374 most cases a storage backed mount point offers the same performance and a lot
377 NOTE: The contents of device mount points are not backed up when using
381 [[pct_container_network]]
385 [thumbnail="screenshot/gui-create-ct-network.png"]
387 You can configure up to 10 network interfaces for a single container.
388 The corresponding options are called `net0` to `net9`, and they can contain the
391 include::pct-network-opts.adoc[]
394 [[pct_startup_and_shutdown]]
395 Automatic Start and Shutdown of Containers
396 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
398 To automatically start a container when the host system boots, select the
399 option 'Start at boot' in the 'Options' panel of the container in the web
400 interface or run the following command:
403 # pct set CTID -onboot 1
406 .Start and Shutdown Order
407 // use the screenshot from qemu - its the same
408 [thumbnail="screenshot/gui-qemu-edit-start-order.png"]
410 If you want to fine tune the boot order of your containers, you can use the
411 following parameters:
413 * *Start/Shutdown order*: Defines the start order priority. For example, set it
414 to 1 if you want the CT to be the first to be started. (We use the reverse
415 startup order for shutdown, so a container with a start order of 1 would be
416 the last to be shut down)
417 * *Startup delay*: Defines the interval between this container start and
418 subsequent containers starts. For example, set it to 240 if you want to wait
419 240 seconds before starting other containers.
420 * *Shutdown timeout*: Defines the duration in seconds {pve} should wait
421 for the container to be offline after issuing a shutdown command.
422 By default this value is set to 60, which means that {pve} will issue a
423 shutdown request, wait 60s for the machine to be offline, and if after 60s
424 the machine is still online will notify that the shutdown action failed.
426 Please note that containers without a Start/Shutdown order parameter will
427 always start after those where the parameter is set, and this parameter only
428 makes sense between the machines running locally on a host, and not
434 You can add a hook script to CTs with the config property `hookscript`.
437 # pct set 100 -hookscript local:snippets/hookscript.pl
440 It will be called during various phases of the guests lifetime. For an example
441 and documentation see the example script under
442 `/usr/share/pve-docs/examples/guest-example-hookscript.pl`.
444 Security Considerations
445 -----------------------
447 Containers use the kernel of the host system. This exposes an attack surface
448 for malicious users. In general, full virtual machines provide better
449 isolation. This should be considered if containers are provided to unknown or
452 To reduce the attack surface, LXC uses many security features like AppArmor,
453 CGroups and kernel namespaces.
458 AppArmor profiles are used to restrict access to possibly dangerous actions.
459 Some system calls, i.e. `mount`, are prohibited from execution.
461 To trace AppArmor activity, use:
464 # dmesg | grep apparmor
467 Although it is not recommended, AppArmor can be disabled for a container. This
468 brings security risks with it. Some syscalls can lead to privilege escalation
469 when executed within a container if the system is misconfigured or if a LXC or
470 Linux Kernel vulnerability exists.
472 To disable AppArmor for a container, add the following line to the container
473 configuration file located at `/etc/pve/lxc/CTID.conf`:
476 lxc.apparmor_profile = unconfined
479 WARNING: Please note that this is not recommended for production use.
482 // TODO: describe cgroups + seccomp a bit more.
483 // TODO: pve-lxc-syscalld
486 Guest Operating System Configuration
487 ------------------------------------
489 {pve} tries to detect the Linux distribution in the container, and modifies
490 some files. Here is a short list of things done at container startup:
492 set /etc/hostname:: to set the container name
494 modify /etc/hosts:: to allow lookup of the local hostname
496 network setup:: pass the complete network setup to the container
498 configure DNS:: pass information about DNS servers
500 adapt the init system:: for example, fix the number of spawned getty processes
502 set the root password:: when creating a new container
504 rewrite ssh_host_keys:: so that each container has unique keys
506 randomize crontab:: so that cron does not start at the same time on all containers
508 Changes made by {PVE} are enclosed by comment markers:
516 Those markers will be inserted at a reasonable location in the file. If such a
517 section already exists, it will be updated in place and will not be moved.
519 Modification of a file can be prevented by adding a `.pve-ignore.` file for it.
520 For instance, if the file `/etc/.pve-ignore.hosts` exists then the `/etc/hosts`
521 file will not be touched. This can be a simple empty file created via:
524 # touch /etc/.pve-ignore.hosts
527 Most modifications are OS dependent, so they differ between different
528 distributions and versions. You can completely disable modifications by
529 manually setting the `ostype` to `unmanaged`.
531 OS type detection is done by testing for certain files inside the
532 container. {pve} first checks the `/etc/os-release` file
533 footnote:[/etc/os-release replaces the multitude of per-distribution
534 release files https://manpages.debian.org/stable/systemd/os-release.5.en.html].
535 If that file is not present, or it does not contain a clearly recognizable
536 distribution identifier the following distribution specific release files are
539 Ubuntu:: inspect /etc/lsb-release (`DISTRIB_ID=Ubuntu`)
541 Debian:: test /etc/debian_version
543 Fedora:: test /etc/fedora-release
545 RedHat or CentOS:: test /etc/redhat-release
547 ArchLinux:: test /etc/arch-release
549 Alpine:: test /etc/alpine-release
551 Gentoo:: test /etc/gentoo-release
553 NOTE: Container start fails if the configured `ostype` differs from the auto
557 [[pct_container_storage]]
561 The {pve} LXC container storage model is more flexible than traditional
562 container storage models. A container can have multiple mount points. This
563 makes it possible to use the best suited storage for each application.
565 For example the root file system of the container can be on slow and cheap
566 storage while the database can be on fast and distributed storage via a second
567 mount point. See section <<pct_mount_points, Mount Points>> for further
570 Any storage type supported by the {pve} storage library can be used. This means
571 that containers can be stored on local (for example `lvm`, `zfs` or directory),
572 shared external (like `iSCSI`, `NFS`) or even distributed storage systems like
573 Ceph. Advanced storage features like snapshots or clones can be used if the
574 underlying storage supports them. The `vzdump` backup tool can use snapshots to
575 provide consistent container backups.
577 Furthermore, local devices or local directories can be mounted directly using
578 'bind mounts'. This gives access to local resources inside a container with
579 practically zero overhead. Bind mounts can be used as an easy way to share data
586 WARNING: Because of existing issues in the Linux kernel's freezer subsystem the
587 usage of FUSE mounts inside a container is strongly advised against, as
588 containers need to be frozen for suspend or snapshot mode backups.
590 If FUSE mounts cannot be replaced by other mounting mechanisms or storage
591 technologies, it is possible to establish the FUSE mount on the Proxmox host
592 and use a bind mount point to make it accessible inside the container.
595 Using Quotas Inside Containers
596 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
598 Quotas allow to set limits inside a container for the amount of disk space that
601 NOTE: This only works on ext4 image based storage types and currently only
602 works with privileged containers.
604 Activating the `quota` option causes the following mount options to be used for
606 `usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0`
608 This allows quotas to be used like on any other system. You can initialize the
609 `/aquota.user` and `/aquota.group` files by running:
616 Then edit the quotas using the `edquota` command. Refer to the documentation of
617 the distribution running inside the container for details.
619 NOTE: You need to run the above commands for every mount point by passing the
620 mount point's path instead of just `/`.
623 Using ACLs Inside Containers
624 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
626 The standard Posix **A**ccess **C**ontrol **L**ists are also available inside
627 containers. ACLs allow you to set more detailed file ownership than the
628 traditional user/group/others model.
631 Backup of Container mount points
632 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
634 To include a mount point in backups, enable the `backup` option for it in the
635 container configuration. For an existing mount point `mp0`
638 mp0: guests:subvol-100-disk-1,mp=/root/files,size=8G
641 add `backup=1` to enable it.
644 mp0: guests:subvol-100-disk-1,mp=/root/files,size=8G,backup=1
647 NOTE: When creating a new mount point in the GUI, this option is enabled by
650 To disable backups for a mount point, add `backup=0` in the way described
651 above, or uncheck the *Backup* checkbox on the GUI.
653 Replication of Containers mount points
654 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
656 By default, additional mount points are replicated when the Root Disk is
657 replicated. If you want the {pve} storage replication mechanism to skip a mount
658 point, you can set the *Skip replication* option for that mount point.
659 As of {pve} 5.0, replication requires a storage of type `zfspool`. Adding a
660 mount point to a different type of storage when the container has replication
661 configured requires to have *Skip replication* enabled for that mount point.
671 It is possible to use the `vzdump` tool for container backup. Please refer to
672 the `vzdump` manual page for details.
675 Restoring Container Backups
676 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
678 Restoring container backups made with `vzdump` is possible using the `pct
679 restore` command. By default, `pct restore` will attempt to restore as much of
680 the backed up container configuration as possible. It is possible to override
681 the backed up configuration by manually setting container options on the
682 command line (see the `pct` manual page for details).
684 NOTE: `pvesm extractconfig` can be used to view the backed up configuration
685 contained in a vzdump archive.
687 There are two basic restore modes, only differing by their handling of mount
691 ``Simple'' Restore Mode
692 ^^^^^^^^^^^^^^^^^^^^^^^
694 If neither the `rootfs` parameter nor any of the optional `mpX` parameters are
695 explicitly set, the mount point configuration from the backed up configuration
696 file is restored using the following steps:
698 . Extract mount points and their options from backup
699 . Create volumes for storage backed mount points (on storage provided with the
700 `storage` parameter, or default local storage if unset)
701 . Extract files from backup archive
702 . Add bind and device mount points to restored configuration (limited to root
705 NOTE: Since bind and device mount points are never backed up, no files are
706 restored in the last step, but only the configuration options. The assumption
707 is that such mount points are either backed up with another mechanism (e.g.,
708 NFS space that is bind mounted into many containers), or not intended to be
711 This simple mode is also used by the container restore operations in the web
715 ``Advanced'' Restore Mode
716 ^^^^^^^^^^^^^^^^^^^^^^^^^
718 By setting the `rootfs` parameter (and optionally, any combination of `mpX`
719 parameters), the `pct restore` command is automatically switched into an
720 advanced mode. This advanced mode completely ignores the `rootfs` and `mpX`
721 configuration options contained in the backup archive, and instead only uses
722 the options explicitly provided as parameters.
724 This mode allows flexible configuration of mount point settings at restore
727 * Set target storages, volume sizes and other options for each mount point
729 * Redistribute backed up files according to new mount point scheme
730 * Restore to device and/or bind mount points (limited to root user)
733 Managing Containers with `pct`
734 ------------------------------
736 The ``Proxmox Container Toolkit'' (`pct`) is the command line tool to manage
737 {pve} containers. It enables you to create or destroy containers, as well as
738 control the container execution (start, stop, reboot, migrate, etc.). It can be
739 used to set parameters in the config file of a container, for example the
740 network configuration or memory limits.
745 Create a container based on a Debian template (provided you have already
746 downloaded the template via the web interface)
749 # pct create 100 /var/lib/vz/template/cache/debian-10.0-standard_10.0-1_amd64.tar.gz
758 Start a login session via getty
764 Enter the LXC namespace and run a shell as root user
770 Display the configuration
776 Add a network interface called `eth0`, bridged to the host bridge `vmbr0`, set
777 the address and gateway, while it's running
780 # pct set 100 -net0 name=eth0,bridge=vmbr0,ip=192.168.15.147/24,gw=192.168.15.1
783 Reduce the memory of the container to 512MB
786 # pct set 100 -memory 512
790 Obtaining Debugging Logs
791 ~~~~~~~~~~~~~~~~~~~~~~~~
793 In case `pct start` is unable to start a specific container, it might be
794 helpful to collect debugging output by running `lxc-start` (replace `ID` with
798 # lxc-start -n ID -F -l DEBUG -o /tmp/lxc-ID.log
801 This command will attempt to start the container in foreground mode, to stop
802 the container run `pct shutdown ID` or `pct stop ID` in a second terminal.
804 The collected debug log is written to `/tmp/lxc-ID.log`.
806 NOTE: If you have changed the container's configuration since the last start
807 attempt with `pct start`, you need to run `pct start` at least once to also
808 update the configuration used by `lxc-start`.
814 If you have a cluster, you can migrate your Containers with
817 # pct migrate <ctid> <target>
820 This works as long as your Container is offline. If it has local volumes or
821 mount points defined, the migration will copy the content over the network to
822 the target host if the same storage is defined there.
824 Running containers cannot live-migrated due to technical limitations. You can
825 do a restart migration, which shuts down, moves and then starts a container
826 again on the target node. As containers are very lightweight, this results
827 normally only in a downtime of some hundreds of milliseconds.
829 A restart migration can be done through the web interface or by using the
830 `--restart` flag with the `pct migrate` command.
832 A restart migration will shut down the Container and kill it after the
833 specified timeout (the default is 180 seconds). Then it will migrate the
834 Container like an offline migration and when finished, it starts the Container
837 [[pct_configuration]]
841 The `/etc/pve/lxc/<CTID>.conf` file stores container configuration, where
842 `<CTID>` is the numeric ID of the given container. Like all other files stored
843 inside `/etc/pve/`, they get automatically replicated to all other cluster
846 NOTE: CTIDs < 100 are reserved for internal purposes, and CTIDs need to be
849 .Example Container Configuration
856 net0: bridge=vmbr0,hwaddr=66:64:66:64:64:36,ip=dhcp,name=eth0,type=veth
857 rootfs: local:107/vm-107-disk-1.raw,size=7G
860 The configuration files are simple text files. You can edit them using a normal
861 text editor, for example, `vi` or `nano`.
862 This is sometimes useful to do small corrections, but keep in mind that you
863 need to restart the container to apply such changes.
865 For that reason, it is usually better to use the `pct` command to generate and
866 modify those files, or do the whole thing using the GUI.
867 Our toolkit is smart enough to instantaneously apply most changes to running
868 containers. This feature is called ``hot plug'', and there is no need to restart
869 the container in that case.
871 In cases where a change cannot be hot-plugged, it will be registered as a
872 pending change (shown in red color in the GUI).
873 They will only be applied after rebooting the container.
879 The container configuration file uses a simple colon separated key/value
880 format. Each line has the following format:
887 Blank lines in those files are ignored, and lines starting with a `#` character
888 are treated as comments and are also ignored.
890 It is possible to add low-level, LXC style configuration directly, for example:
893 lxc.init_cmd: /sbin/my_own_init
899 lxc.init_cmd = /sbin/my_own_init
902 The settings are passed directly to the LXC low-level tools.
909 When you create a snapshot, `pct` stores the configuration at snapshot time
910 into a separate snapshot section within the same configuration file. For
911 example, after creating a snapshot called ``testsnapshot'', your configuration
912 file will look like this:
914 .Container configuration with snapshot
928 There are a few snapshot related properties like `parent` and `snaptime`. The
929 `parent` property is used to store the parent/child relationship between
930 snapshots. `snaptime` is the snapshot creation time stamp (Unix epoch).
937 include::pct.conf.5-opts.adoc[]
943 Container migrations, snapshots and backups (`vzdump`) set a lock to prevent
944 incompatible concurrent actions on the affected container. Sometimes you need
945 to remove such a lock manually (e.g., after a power failure).
951 CAUTION: Only do this if you are sure the action which set the lock is no
960 `/etc/pve/lxc/<CTID>.conf`::
962 Configuration file for the container '<CTID>'.
965 include::pve-copyright.adoc[]