+[[chapter_pct]]
ifdef::manvolnum[]
-PVE({manvolnum})
-================
-include::attributes.txt[]
+pct(1)
+======
+:pve-toplevel:
NAME
----
pct - Tool to manage Linux Containers (LXC) on Proxmox VE
-SYNOPSYS
+SYNOPSIS
--------
include::pct.1-synopsis.adoc[]
ifndef::manvolnum[]
Proxmox Container Toolkit
=========================
-include::attributes.txt[]
+:pve-toplevel:
endif::manvolnum[]
+ifdef::wiki[]
+:title: Linux Container
+endif::wiki[]
+Containers are a lightweight alternative to fully virtualized machines (VMs).
+They use the kernel of the host system that they run on, instead of emulating a
+full operating system (OS). This means that containers can access resources on
+the host system directly.
-Containers are a lightweight alternative to fully virtualized
-VMs. Instead of emulating a complete Operating System (OS), containers
-simply use the OS of the host they run on. This implies that all
-containers use the same kernel, and that they can access resources
-from the host directly.
+The runtime costs for containers is low, usually negligible. However, there are
+some drawbacks that need be considered:
-This is great because containers do not waste CPU power nor memory due
-to kernel emulation. Container run-time costs are close to zero and
-usually negligible. But there are also some drawbacks you need to
-consider:
+* Only Linux distributions can be run in Proxmox Containers. It is not possible to run
+ other operating systems like, for example, FreeBSD or Microsoft Windows
+ inside a container.
-* You can only run Linux based OS inside containers, i.e. it is not
- possible to run FreeBSD or MS Windows inside.
+* For security reasons, access to host resources needs to be restricted.
+ Therefore, containers run in their own separate namespaces. Additionally some
+ syscalls (user space requests to the Linux kernel) are not allowed within containers.
-* For security reasons, access to host resources needs to be
- restricted. This is done with AppArmor, SecComp filters and other
- kernel features. Be prepared that some syscalls are not allowed
- inside containers.
+{pve} uses https://linuxcontainers.org/lxc/introduction/[Linux Containers (LXC)] as its underlying
+container technology. The ``Proxmox Container Toolkit'' (`pct`) simplifies the
+usage and management of LXC, by providing an interface that abstracts
+complex tasks.
-{pve} uses https://linuxcontainers.org/[LXC] as underlying container
-technology. We consider LXC as low-level library, which provides
-countless options. It would be too difficult to use those tools
-directly. Instead, we provide a small wrapper called `pct`, the
-"Proxmox Container Toolkit".
+Containers are tightly integrated with {pve}. This means that they are aware of
+the cluster setup, and they can use the same network and storage resources as
+virtual machines. You can also use the {pve} firewall, or manage containers
+using the HA framework.
-The toolkit is tightly coupled with {pve}. That means that it is aware
-of the cluster setup, and it can use the same network and storage
-resources as fully virtualized VMs. You can even use the {pve}
-firewall, or manage containers using the HA framework.
+Our primary goal is to offer an environment that provides the benefits of using a
+VM, but without the additional overhead. This means that Proxmox Containers can
+be categorized as ``System Containers'', rather than ``Application Containers''.
-Our primary goal is to offer an environment as one would get from a
-VM, but without the additional overhead. We call this "System
-Containers".
+NOTE: If you want to run application containers, for example, 'Docker' images, it
+is recommended that you run them inside a Proxmox QEMU VM. This will give you
+all the advantages of application containerization, while also providing the
+benefits that VMs offer, such as strong isolation from the host and the ability
+to live-migrate, which otherwise isn't possible with containers.
-NOTE: If you want to run micro-containers (with docker, rkt, ...), it
-is best to run them inside a VM.
+Technology Overview
+-------------------
-Security Considerations
------------------------
-
-Containers use the same kernel as the host, so there is a big attack
-surface for malicious users. You should consider this fact if you
-provide containers to totally untrusted people. In general, fully
-virtualized VMs provide better isolation.
+* LXC (https://linuxcontainers.org/)
-The good news is that LXC uses many kernel security features like
-AppArmor, CGroups and PID and user namespaces, which makes containers
-usage quite secure. We distinguish two types of containers:
+* Integrated into {pve} graphical web user interface (GUI)
+* Easy to use command-line tool `pct`
-Privileged Containers
-~~~~~~~~~~~~~~~~~~~~~
+* Access via {pve} REST API
-Security is done by dropping capabilities, using mandatory access
-control (AppArmor), SecComp filters and namespaces. The LXC team
-considers this kind of container as unsafe, and they will not consider
-new container escape exploits to be security issues worthy of a CVE
-and quick fix. So you should use this kind of containers only inside a
-trusted environment, or when no untrusted task is running as root in
-the container.
+* 'lxcfs' to provide containerized /proc file system
+* Control groups ('cgroups') for resource isolation and limitation
-Unprivileged Containers
-~~~~~~~~~~~~~~~~~~~~~~~
+* 'AppArmor' and 'seccomp' to improve security
-This kind of containers use a new kernel feature called user
-namespaces. The root UID 0 inside the container is mapped to an
-unprivileged user outside the container. This means that most security
-issues (container escape, resource abuse, ...) in those containers
-will affect a random unprivileged user, and so would be a generic
-kernel security bug rather than an LXC issue. The LXC team thinks
-unprivileged containers are safe by design.
+* Modern Linux kernels
+* Image based deployment (xref:pct_supported_distributions[templates])
-Configuration
--------------
+* Uses {pve} xref:chapter_storage[storage library]
-The `/etc/pve/lxc/<CTID>.conf` file stores container configuration,
-where `<CTID>` is the numeric ID of the given container. Like all
-other files stored inside `/etc/pve/`, they get automatically
-replicated to all other cluster nodes.
+* Container setup from host (network, DNS, storage, etc.)
-NOTE: CTIDs < 100 are reserved for internal purposes, and CTIDs need to be
-unique cluster wide.
-.Example Container Configuration
-----
-ostype: debian
-arch: amd64
-hostname: www
-memory: 512
-swap: 512
-net0: bridge=vmbr0,hwaddr=66:64:66:64:64:36,ip=dhcp,name=eth0,type=veth
-rootfs: local:107/vm-107-disk-1.raw,size=7G
-----
-
-Those configuration files are simple text files, and you can edit them
-using a normal text editor (`vi`, `nano`, ...). This is sometimes
-useful to do small corrections, but keep in mind that you need to
-restart the container to apply such changes.
+[[pct_supported_distributions]]
+Supported Distributions
+-----------------------
-For that reason, it is usually better to use the `pct` command to
-generate and modify those files, or do the whole thing using the GUI.
-Our toolkit is smart enough to instantaneously apply most changes to
-running containers. This feature is called "hot plug", and there is no
-need to restart the container in that case.
+List of officially supported distributions can be found below.
+Templates for the following distributions are available through our
+repositories. You can use xref:pct_container_images[pveam] tool or the
+Graphical User Interface to download them.
-File Format
-~~~~~~~~~~~
+Alpine Linux
+~~~~~~~~~~~~
-Container configuration files use a simple colon separated key/value
-format. Each line has the following format:
+[quote, 'https://alpinelinux.org']
+____
+Alpine Linux is a security-oriented, lightweight Linux distribution based on
+musl libc and busybox.
+____
- # this is a comment
- OPTION: value
+For currently supported releases see:
-Blank lines in those files are ignored, and lines starting with a `#`
-character are treated as comments and are also ignored.
+https://alpinelinux.org/releases/
-It is possible to add low-level, LXC style configuration directly, for
-example:
+Arch Linux
+~~~~~~~~~~
- lxc.init_cmd: /sbin/my_own_init
+[quote, 'https://archlinux.org/']
+____
+Arch Linux, a lightweight and flexible Linux® distribution that tries to Keep It Simple.
+____
-or
+Arch Linux is using a rolling-release model, see its wiki for more details:
- lxc.init_cmd = /sbin/my_own_init
+https://wiki.archlinux.org/title/Arch_Linux
-Those settings are directly passed to the LXC low-level tools.
+CentOS, Almalinux, Rocky Linux
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+CentOS / CentOS Stream
+^^^^^^^^^^^^^^^^^^^^^^
-Snapshots
-~~~~~~~~~
+[quote, 'https://centos.org']
+____
+The CentOS Linux distribution is a stable, predictable, manageable and
+reproducible platform derived from the sources of Red Hat Enterprise Linux
+(RHEL)
+____
-When you create a snapshot, `pct` stores the configuration at snapshot
-time into a separate snapshot section within the same configuration
-file. For example, after creating a snapshot called ``testsnapshot'',
-your configuration file will look like this:
+For currently supported releases see:
-.Container configuration with snapshot
-----
-memory: 512
-swap: 512
-parent: testsnaphot
-...
+https://en.wikipedia.org/wiki/CentOS#End-of-support_schedule
-[testsnaphot]
-memory: 512
-swap: 512
-snaptime: 1457170803
-...
-----
+Almalinux
+^^^^^^^^^
-There are a few snapshot related properties like `parent` and
-`snaptime`. The `parent` property is used to store the parent/child
-relationship between snapshots. `snaptime` is the snapshot creation
-time stamp (Unix epoch).
+[quote, 'https://almalinux.org']
+____
+An Open Source, community owned and governed, forever-free enterprise Linux
+distribution, focused on long-term stability, providing a robust
+production-grade platform. AlmaLinux OS is 1:1 binary compatible with RHEL® and
+pre-Stream CentOS.
+____
-Guest Operating System Configuration
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+For currently supported releases see:
-We normally try to detect the operating system type inside the
-container, and then modify some files inside the container to make
-them work as expected. Here is a short list of things we do at
-container startup:
+https://en.wikipedia.org/wiki/AlmaLinux#Releases
-set /etc/hostname:: to set the container name
+Rocky Linux
+^^^^^^^^^^^
-modify /etc/hosts:: to allow lookup of the local hostname
+[quote, 'https://rockylinux.org']
+____
+Rocky Linux is a community enterprise operating system designed to be 100%
+bug-for-bug compatible with America's top enterprise Linux distribution now
+that its downstream partner has shifted direction.
+____
-network setup:: pass the complete network setup to the container
+For currently supported releases see:
-configure DNS:: pass information about DNS servers
+https://en.wikipedia.org/wiki/Rocky_Linux#Releases
-adapt the init system:: for example, fix the number of spawned getty processes
+Debian
+~~~~~~
-set the root password:: when creating a new container
+[quote, 'https://www.debian.org/intro/index#software']
+____
+Debian is a free operating system, developed and maintained by the Debian
+project. A free Linux distribution with thousands of applications to meet our
+users' needs.
+____
-rewrite ssh_host_keys:: so that each container has unique keys
+For currently supported releases see:
-randomize crontab:: so that cron does not start at the same time on all containers
+https://www.debian.org/releases/stable/releasenotes
-Changes made by {PVE} are enclosed by comment markers:
+Devuan
+~~~~~~
-----
-# --- BEGIN PVE ---
-<data>
-# --- END PVE ---
-----
+[quote, 'https://www.devuan.org']
+____
+Devuan GNU+Linux is a fork of Debian without systemd that allows users to
+reclaim control over their system by avoiding unnecessary entanglements and
+ensuring Init Freedom.
+____
-Those markers will be inserted at a reasonable location in the
-file. If such a section already exists, it will be updated in place
-and will not be moved.
+For currently supported releases see:
-Modification of a file can be prevented by adding a `.pve-ignore.`
-file for it. For instance, if the file `/etc/.pve-ignore.hosts`
-exists then the `/etc/hosts` file will not be touched. This can be a
-simple empty file creatd via:
+https://www.devuan.org/os/releases
- # touch /etc/.pve-ignore.hosts
+Fedora
+~~~~~~
-Most modifications are OS dependent, so they differ between different
-distributions and versions. You can completely disable modifications
-by manually setting the `ostype` to `unmanaged`.
+[quote, 'https://getfedora.org']
+____
+Fedora creates an innovative, free, and open source platform for hardware,
+clouds, and containers that enables software developers and community members
+to build tailored solutions for their users.
+____
-OS type detection is done by testing for certain files inside the
-container:
+For currently supported releases see:
-Ubuntu:: inspect /etc/lsb-release (`DISTRIB_ID=Ubuntu`)
+https://fedoraproject.org/wiki/Releases
-Debian:: test /etc/debian_version
+Gentoo
+~~~~~~
-Fedora:: test /etc/fedora-release
+[quote, 'https://www.gentoo.org']
+____
+a highly flexible, source-based Linux distribution.
+____
-RedHat or CentOS:: test /etc/redhat-release
+Gentoo is using a rolling-release model.
-ArchLinux:: test /etc/arch-release
+OpenSUSE
+~~~~~~~~
-Alpine:: test /etc/alpine-release
+[quote, 'https://www.opensuse.org']
+____
+The makers' choice for sysadmins, developers and desktop users.
+____
-Gentoo:: test /etc/gentoo-release
+For currently supported releases see:
-NOTE: Container start fails if the configured `ostype` differs from the auto
-detected type.
+https://get.opensuse.org/leap/
+Ubuntu
+~~~~~~
-Options
-~~~~~~~
+[quote, 'https://ubuntu.com/']
+____
+Ubuntu is the modern, open source operating system on Linux for the enterprise
+server, desktop, cloud, and IoT.
+____
-include::pct.conf.5-opts.adoc[]
+For currently supported releases see:
+https://wiki.ubuntu.com/Releases
+[[pct_container_images]]
Container Images
----------------
Container images, sometimes also referred to as ``templates'' or
-``appliances'', are `tar` archives which contain everything to run a
-container. You can think of it as a tidy container backup. Like most
-modern container toolkits, `pct` uses those images when you create a
-new container, for example:
+``appliances'', are `tar` archives which contain everything to run a container.
- pct create 999 local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz
+{pve} itself provides a variety of basic templates for the
+xref:pct_supported_distributions[most common Linux distributions]. They can be
+downloaded using the GUI or the `pveam` (short for {pve} Appliance Manager)
+command-line utility. Additionally, https://www.turnkeylinux.org/[TurnKey
+Linux] container templates are also available to download.
-Proxmox itself ships a set of basic templates for most common
-operating systems, and you can download them using the `pveam` (short
-for {pve} Appliance Manager) command line utility. You can also
-download https://www.turnkeylinux.org/[TurnKey Linux] containers using
-that tool (or the graphical user interface).
+The list of available templates is updated daily through the 'pve-daily-update'
+timer. You can also trigger an update manually by executing:
-Our image repositories contain a list of available images, and there
-is a cron job run each day to download that list. You can trigger that
-update manually with:
-
- pveam update
+----
+# pveam update
+----
-After that you can view the list of available images using:
+To view the list of available images run:
- pveam available
+----
+# pveam available
+----
You can restrict this large list by specifying the `section` you are
interested in, for example basic `system` images:
.List available system images
----
# pveam available --section system
-system archlinux-base_2015-24-29-1_x86_64.tar.gz
-system centos-7-default_20160205_amd64.tar.xz
-system debian-6.0-standard_6.0-7_amd64.tar.gz
-system debian-7.0-standard_7.0-3_amd64.tar.gz
-system debian-8.0-standard_8.0-1_amd64.tar.gz
-system ubuntu-12.04-standard_12.04-1_amd64.tar.gz
-system ubuntu-14.04-standard_14.04-1_amd64.tar.gz
-system ubuntu-15.04-standard_15.04-1_amd64.tar.gz
-system ubuntu-15.10-standard_15.10-1_amd64.tar.gz
+system alpine-3.12-default_20200823_amd64.tar.xz
+system alpine-3.13-default_20210419_amd64.tar.xz
+system alpine-3.14-default_20210623_amd64.tar.xz
+system archlinux-base_20210420-1_amd64.tar.gz
+system centos-7-default_20190926_amd64.tar.xz
+system centos-8-default_20201210_amd64.tar.xz
+system debian-9.0-standard_9.7-1_amd64.tar.gz
+system debian-10-standard_10.7-1_amd64.tar.gz
+system devuan-3.0-standard_3.0_amd64.tar.gz
+system fedora-33-default_20201115_amd64.tar.xz
+system fedora-34-default_20210427_amd64.tar.xz
+system gentoo-current-default_20200310_amd64.tar.xz
+system opensuse-15.2-default_20200824_amd64.tar.xz
+system ubuntu-16.04-standard_16.04.5-1_amd64.tar.gz
+system ubuntu-18.04-standard_18.04.1-1_amd64.tar.gz
+system ubuntu-20.04-standard_20.04-1_amd64.tar.gz
+system ubuntu-20.10-standard_20.10-1_amd64.tar.gz
+system ubuntu-21.04-standard_21.04-1_amd64.tar.gz
----
-Before you can use such a template, you need to download them into one
-of your storages. You can simply use storage `local` for that
-purpose. For clustered installations, it is preferred to use a shared
-storage so that all nodes can access those images.
+Before you can use such a template, you need to download them into one of your
+storages. If you're unsure to which one, you can simply use the `local` named
+storage for that purpose. For clustered installations, it is preferred to use a
+shared storage so that all nodes can access those images.
- pveam download local debian-8.0-standard_8.0-1_amd64.tar.gz
+----
+# pveam download local debian-10.0-standard_10.0-1_amd64.tar.gz
+----
-You are now ready to create containers using that image, and you can
-list all downloaded images on storage `local` with:
+You are now ready to create containers using that image, and you can list all
+downloaded images on storage `local` with:
----
# pveam list local
-local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz 190.20MB
+local:vztmpl/debian-10.0-standard_10.0-1_amd64.tar.gz 219.95MB
----
-The above command shows you the full {pve} volume identifiers. They include
-the storage name, and most other {pve} commands can use them. For
-example you can delete that image later with:
+TIP: You can also use the {pve} web interface GUI to download, list and delete
+container templates.
- pveam remove local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz
+`pct` uses them to create a new container, for example:
+----
+# pct create 999 local:vztmpl/debian-10.0-standard_10.0-1_amd64.tar.gz
+----
-Container Storage
------------------
+The above command shows you the full {pve} volume identifiers. They include the
+storage name, and most other {pve} commands can use them. For example you can
+delete that image later with:
+
+----
+# pveam remove local:vztmpl/debian-10.0-standard_10.0-1_amd64.tar.gz
+----
+
+
+[[pct_settings]]
+Container Settings
+------------------
+
+[[pct_general]]
+General Settings
+~~~~~~~~~~~~~~~~
+
+[thumbnail="screenshot/gui-create-ct-general.png"]
-Traditional containers use a very simple storage model, only allowing
-a single mount point, the root file system. This was further
-restricted to specific file system types like `ext4` and `nfs`.
-Additional mounts are often done by user provided scripts. This turned
-out to be complex and error prone, so we try to avoid that now.
-
-Our new LXC based container model is more flexible regarding
-storage. First, you can have more than a single mount point. This
-allows you to choose a suitable storage for each application. For
-example, you can use a relatively slow (and thus cheap) storage for
-the container root file system. Then you can use a second mount point
-to mount a very fast, distributed storage for your database
-application.
-
-The second big improvement is that you can use any storage type
-supported by the {pve} storage library. That means that you can store
-your containers on local `lvmthin` or `zfs`, shared `iSCSI` storage,
-or even on distributed storage systems like `ceph`. It also enables us
-to use advanced storage features like snapshots and clones. `vzdump`
-can also use the snapshot feature to provide consistent container
-backups.
-
-Last but not least, you can also mount local devices directly, or
-mount local directories using bind mounts. That way you can access
-local storage inside containers with zero overhead. Such bind mounts
-also provide an easy way to share data between different containers.
+General settings of a container include
+* the *Node* : the physical server on which the container will run
+* the *CT ID*: a unique number in this {pve} installation used to identify your
+ container
+* *Hostname*: the hostname of the container
+* *Resource Pool*: a logical group of containers and VMs
+* *Password*: the root password of the container
+* *SSH Public Key*: a public key for connecting to the root account over SSH
+* *Unprivileged container*: this option allows to choose at creation time
+ if you want to create a privileged or unprivileged container.
+Unprivileged Containers
+^^^^^^^^^^^^^^^^^^^^^^^
+
+Unprivileged containers use a new kernel feature called user namespaces.
+The root UID 0 inside the container is mapped to an unprivileged user outside
+the container. This means that most security issues (container escape, resource
+abuse, etc.) in these containers will affect a random unprivileged user, and
+would be a generic kernel security bug rather than an LXC issue. The LXC team
+thinks unprivileged containers are safe by design.
+
+This is the default option when creating a new container.
+
+NOTE: If the container uses systemd as an init system, please be aware the
+systemd version running inside the container should be equal to or greater than
+220.
+
+
+Privileged Containers
+^^^^^^^^^^^^^^^^^^^^^
+
+Security in containers is achieved by using mandatory access control 'AppArmor'
+restrictions, 'seccomp' filters and Linux kernel namespaces. The LXC team
+considers this kind of container as unsafe, and they will not consider new
+container escape exploits to be security issues worthy of a CVE and quick fix.
+That's why privileged containers should only be used in trusted environments.
+
+
+[[pct_cpu]]
+CPU
+~~~
+
+[thumbnail="screenshot/gui-create-ct-cpu.png"]
+
+You can restrict the number of visible CPUs inside the container using the
+`cores` option. This is implemented using the Linux 'cpuset' cgroup
+(**c**ontrol *group*).
+A special task inside `pvestatd` tries to distribute running containers among
+available CPUs periodically.
+To view the assigned CPUs run the following command:
+
+----
+# pct cpusets
+ ---------------------
+ 102: 6 7
+ 105: 2 3 4 5
+ 108: 0 1
+ ---------------------
+----
+
+Containers use the host kernel directly. All tasks inside a container are
+handled by the host CPU scheduler. {pve} uses the Linux 'CFS' (**C**ompletely
+**F**air **S**cheduler) scheduler by default, which has additional bandwidth
+control options.
+
+[horizontal]
+
+`cpulimit`: :: You can use this option to further limit assigned CPU time.
+Please note that this is a floating point number, so it is perfectly valid to
+assign two cores to a container, but restrict overall CPU consumption to half a
+core.
++
+----
+cores: 2
+cpulimit: 0.5
+----
+
+`cpuunits`: :: This is a relative weight passed to the kernel scheduler. The
+larger the number is, the more CPU time this container gets. Number is relative
+to the weights of all the other running containers. The default is `100` (or
+`1024` if the host uses legacy cgroup v1). You can use this setting to
+prioritize some containers.
+
+
+[[pct_memory]]
+Memory
+~~~~~~
+
+[thumbnail="screenshot/gui-create-ct-memory.png"]
+
+Container memory is controlled using the cgroup memory controller.
+
+[horizontal]
+
+`memory`: :: Limit overall memory usage. This corresponds to the
+`memory.limit_in_bytes` cgroup setting.
+
+`swap`: :: Allows the container to use additional swap memory from the host
+swap space. This corresponds to the `memory.memsw.limit_in_bytes` cgroup
+setting, which is set to the sum of both value (`memory + swap`).
+
+
+[[pct_mount_points]]
Mount Points
~~~~~~~~~~~~
-The root mount point is configured with the `rootfs` property, and you can
-configure up to 10 additional mount points. The corresponding options
-are called `mp0` to `mp9`, and they can contain the following setting:
+[thumbnail="screenshot/gui-create-ct-root-disk.png"]
+
+The root mount point is configured with the `rootfs` property. You can
+configure up to 256 additional mount points. The corresponding options are
+called `mp0` to `mp255`. They can contain the following settings:
include::pct-mountpoint-opts.adoc[]
-Currently there are basically three types of mount points: storage backed
-mount points, bind mounts and device mounts.
+Currently there are three types of mount points: storage backed mount points,
+bind mounts, and device mounts.
.Typical container `rootfs` configuration
----
- Directories: passing `size=0` triggers a special case where instead of a raw
image a directory is created.
+NOTE: The special option syntax `STORAGE_ID:SIZE_IN_GB` for storage backed
+mount point volumes will automatically allocate a volume of the specified size
+on the specified storage. For example, calling
+
+----
+pct set 100 -mp0 thin1:10,mp=/path/in/container
+----
+
+will allocate a 10GB volume on the storage `thin1` and replace the volume ID
+place holder `10` with the allocated volume ID, and setup the moutpoint in the
+container at `/path/in/container`
+
Bind Mount Points
^^^^^^^^^^^^^^^^^
NOTE: The contents of bind mount points are not backed up when using `vzdump`.
-WARNING: For security reasons, bind mounts should only be established
-using source directories especially reserved for this purpose, e.g., a
-directory hierarchy under `/mnt/bindmounts`. Never bind mount system
-directories like `/`, `/var` or `/etc` into a container - this poses a
-great security risk.
+WARNING: For security reasons, bind mounts should only be established using
+source directories especially reserved for this purpose, e.g., a directory
+hierarchy under `/mnt/bindmounts`. Never bind mount system directories like
+`/`, `/var` or `/etc` into a container - this poses a great security risk.
NOTE: The bind mount source path must not contain any symlinks.
For example, to make the directory `/mnt/bindmounts/shared` accessible in the
-container with ID `100` under the path `/shared`, use a configuration line like
-`mp0: /mnt/bindmounts/shared,mp=/shared` in `/etc/pve/lxc/100.conf`.
-Alternatively, use `pct set 100 -mp0 /mnt/bindmounts/shared,mp=/shared` to
-achieve the same result.
+container with ID `100` under the path `/shared`, add a configuration line such as:
+
+----
+mp0: /mnt/bindmounts/shared,mp=/shared
+----
+
+into `/etc/pve/lxc/100.conf`.
+
+Or alternatively use the `pct` tool:
+
+----
+pct set 100 -mp0 /mnt/bindmounts/shared,mp=/shared
+----
+
+to achieve the same result.
Device Mount Points
most cases a storage backed mount point offers the same performance and a lot
more features.
-NOTE: The contents of device mount points are not backed up when using `vzdump`.
+NOTE: The contents of device mount points are not backed up when using
+`vzdump`.
+
+
+[[pct_container_network]]
+Network
+~~~~~~~
+
+[thumbnail="screenshot/gui-create-ct-network.png"]
+
+You can configure up to 10 network interfaces for a single container.
+The corresponding options are called `net0` to `net9`, and they can contain the
+following setting:
+
+include::pct-network-opts.adoc[]
+
+
+[[pct_startup_and_shutdown]]
+Automatic Start and Shutdown of Containers
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To automatically start a container when the host system boots, select the
+option 'Start at boot' in the 'Options' panel of the container in the web
+interface or run the following command:
+
+----
+# pct set CTID -onboot 1
+----
+
+.Start and Shutdown Order
+// use the screenshot from qemu - its the same
+[thumbnail="screenshot/gui-qemu-edit-start-order.png"]
+
+If you want to fine tune the boot order of your containers, you can use the
+following parameters:
+
+* *Start/Shutdown order*: Defines the start order priority. For example, set it
+ to 1 if you want the CT to be the first to be started. (We use the reverse
+ startup order for shutdown, so a container with a start order of 1 would be
+ the last to be shut down)
+* *Startup delay*: Defines the interval between this container start and
+ subsequent containers starts. For example, set it to 240 if you want to wait
+ 240 seconds before starting other containers.
+* *Shutdown timeout*: Defines the duration in seconds {pve} should wait
+ for the container to be offline after issuing a shutdown command.
+ By default this value is set to 60, which means that {pve} will issue a
+ shutdown request, wait 60s for the machine to be offline, and if after 60s
+ the machine is still online will notify that the shutdown action failed.
+
+Please note that containers without a Start/Shutdown order parameter will
+always start after those where the parameter is set, and this parameter only
+makes sense between the machines running locally on a host, and not
+cluster-wide.
+
+If you require a delay between the host boot and the booting of the first
+container, see the section on
+xref:first_guest_boot_delay[Proxmox VE Node Management].
+
+
+Hookscripts
+~~~~~~~~~~~
+
+You can add a hook script to CTs with the config property `hookscript`.
+
+----
+# pct set 100 -hookscript local:snippets/hookscript.pl
+----
+
+It will be called during various phases of the guests lifetime. For an example
+and documentation see the example script under
+`/usr/share/pve-docs/examples/guest-example-hookscript.pl`.
+
+Security Considerations
+-----------------------
+
+Containers use the kernel of the host system. This exposes an attack surface
+for malicious users. In general, full virtual machines provide better
+isolation. This should be considered if containers are provided to unknown or
+untrusted people.
+
+To reduce the attack surface, LXC uses many security features like AppArmor,
+CGroups and kernel namespaces.
+
+AppArmor
+~~~~~~~~
+
+AppArmor profiles are used to restrict access to possibly dangerous actions.
+Some system calls, i.e. `mount`, are prohibited from execution.
+
+To trace AppArmor activity, use:
+
+----
+# dmesg | grep apparmor
+----
+
+Although it is not recommended, AppArmor can be disabled for a container. This
+brings security risks with it. Some syscalls can lead to privilege escalation
+when executed within a container if the system is misconfigured or if a LXC or
+Linux Kernel vulnerability exists.
+
+To disable AppArmor for a container, add the following line to the container
+configuration file located at `/etc/pve/lxc/CTID.conf`:
+
+----
+lxc.apparmor.profile = unconfined
+----
+
+WARNING: Please note that this is not recommended for production use.
+
+
+[[pct_cgroup]]
+Control Groups ('cgroup')
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+'cgroup' is a kernel
+mechanism used to hierarchically organize processes and distribute system
+resources.
+
+The main resources controlled via 'cgroups' are CPU time, memory and swap
+limits, and access to device nodes. 'cgroups' are also used to "freeze" a
+container before taking snapshots.
+
+There are 2 versions of 'cgroups' currently available,
+https://www.kernel.org/doc/html/v5.11/admin-guide/cgroup-v1/index.html[legacy]
+and
+https://www.kernel.org/doc/html/v5.11/admin-guide/cgroup-v2.html['cgroupv2'].
+
+Since {pve} 7.0, the default is a pure 'cgroupv2' environment. Previously a
+"hybrid" setup was used, where resource control was mainly done in 'cgroupv1'
+with an additional 'cgroupv2' controller which could take over some subsystems
+via the 'cgroup_no_v1' kernel command-line parameter. (See the
+https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html[kernel
+parameter documentation] for details.)
+
+[[pct_cgroup_compat]]
+CGroup Version Compatibility
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+The main difference between pure 'cgroupv2' and the old hybrid environments
+regarding {pve} is that with 'cgroupv2' memory and swap are now controlled
+independently. The memory and swap settings for containers can map directly to
+these values, whereas previously only the memory limit and the limit of the
+*sum* of memory and swap could be limited.
+
+Another important difference is that the 'devices' controller is configured in a
+completely different way. Because of this, file system quotas are currently not
+supported in a pure 'cgroupv2' environment.
+
+'cgroupv2' support by the container's OS is needed to run in a pure 'cgroupv2'
+environment. Containers running 'systemd' version 231 or newer support
+'cgroupv2' footnote:[this includes all newest major versions of container
+templates shipped by {pve}], as do containers not using 'systemd' as init
+system footnote:[for example Alpine Linux].
+
+[NOTE]
+====
+CentOS 7 and Ubuntu 16.10 are two prominent Linux distributions releases,
+which have a 'systemd' version that is too old to run in a 'cgroupv2'
+environment, you can either
+
+* Upgrade the whole distribution to a newer release. For the examples above, that
+ could be Ubuntu 18.04 or 20.04, and CentOS 8 (or RHEL/CentOS derivatives like
+ AlmaLinux or Rocky Linux). This has the benefit to get the newest bug and
+ security fixes, often also new features, and moving the EOL date in the future.
+
+* Upgrade the Containers systemd version. If the distribution provides a
+ backports repository this can be an easy and quick stop-gap measurement.
+
+* Move the container, or its services, to a Virtual Machine. Virtual Machines
+ have a much less interaction with the host, that's why one can install
+ decades old OS versions just fine there.
+
+* Switch back to the legacy 'cgroup' controller. Note that while it can be a
+ valid solution, it's not a permanent one. Starting from {pve} 9.0, the legacy
+ controller will not be supported anymore.
+====
+
+[[pct_cgroup_change_version]]
+Changing CGroup Version
+^^^^^^^^^^^^^^^^^^^^^^^
+
+TIP: If file system quotas are not required and all containers support 'cgroupv2',
+it is recommended to stick to the new default.
+
+To switch back to the previous version the following kernel command-line
+parameter can be used:
+
+----
+systemd.unified_cgroup_hierarchy=0
+----
+
+See xref:sysboot_edit_kernel_cmdline[this section] on editing the kernel boot
+command line on where to add the parameter.
+
+// TODO: seccomp a bit more.
+// TODO: pve-lxc-syscalld
+
+
+Guest Operating System Configuration
+------------------------------------
+
+{pve} tries to detect the Linux distribution in the container, and modifies
+some files. Here is a short list of things done at container startup:
+
+set /etc/hostname:: to set the container name
+
+modify /etc/hosts:: to allow lookup of the local hostname
+
+network setup:: pass the complete network setup to the container
+
+configure DNS:: pass information about DNS servers
+
+adapt the init system:: for example, fix the number of spawned getty processes
+
+set the root password:: when creating a new container
+
+rewrite ssh_host_keys:: so that each container has unique keys
+
+randomize crontab:: so that cron does not start at the same time on all containers
+
+Changes made by {PVE} are enclosed by comment markers:
+
+----
+# --- BEGIN PVE ---
+<data>
+# --- END PVE ---
+----
+
+Those markers will be inserted at a reasonable location in the file. If such a
+section already exists, it will be updated in place and will not be moved.
+
+Modification of a file can be prevented by adding a `.pve-ignore.` file for it.
+For instance, if the file `/etc/.pve-ignore.hosts` exists then the `/etc/hosts`
+file will not be touched. This can be a simple empty file created via:
+
+----
+# touch /etc/.pve-ignore.hosts
+----
+
+Most modifications are OS dependent, so they differ between different
+distributions and versions. You can completely disable modifications by
+manually setting the `ostype` to `unmanaged`.
+
+OS type detection is done by testing for certain files inside the
+container. {pve} first checks the `/etc/os-release` file
+footnote:[/etc/os-release replaces the multitude of per-distribution
+release files https://manpages.debian.org/stable/systemd/os-release.5.en.html].
+If that file is not present, or it does not contain a clearly recognizable
+distribution identifier the following distribution specific release files are
+checked.
+
+Ubuntu:: inspect /etc/lsb-release (`DISTRIB_ID=Ubuntu`)
+
+Debian:: test /etc/debian_version
+
+Fedora:: test /etc/fedora-release
+
+RedHat or CentOS:: test /etc/redhat-release
+
+ArchLinux:: test /etc/arch-release
+
+Alpine:: test /etc/alpine-release
+
+Gentoo:: test /etc/gentoo-release
+
+NOTE: Container start fails if the configured `ostype` differs from the auto
+detected type.
+
+
+[[pct_container_storage]]
+Container Storage
+-----------------
+
+The {pve} LXC container storage model is more flexible than traditional
+container storage models. A container can have multiple mount points. This
+makes it possible to use the best suited storage for each application.
+
+For example the root file system of the container can be on slow and cheap
+storage while the database can be on fast and distributed storage via a second
+mount point. See section <<pct_mount_points, Mount Points>> for further
+details.
+
+Any storage type supported by the {pve} storage library can be used. This means
+that containers can be stored on local (for example `lvm`, `zfs` or directory),
+shared external (like `iSCSI`, `NFS`) or even distributed storage systems like
+Ceph. Advanced storage features like snapshots or clones can be used if the
+underlying storage supports them. The `vzdump` backup tool can use snapshots to
+provide consistent container backups.
+
+Furthermore, local devices or local directories can be mounted directly using
+'bind mounts'. This gives access to local resources inside a container with
+practically zero overhead. Bind mounts can be used as an easy way to share data
+between containers.
FUSE Mounts
~~~~~~~~~~~
-WARNING: Because of existing issues in the Linux kernel's freezer
-subsystem the usage of FUSE mounts inside a container is strongly
-advised against, as containers need to be frozen for suspend or
-snapshot mode backups.
+WARNING: Because of existing issues in the Linux kernel's freezer subsystem the
+usage of FUSE mounts inside a container is strongly advised against, as
+containers need to be frozen for suspend or snapshot mode backups.
If FUSE mounts cannot be replaced by other mounting mechanisms or storage
technologies, it is possible to establish the FUSE mount on the Proxmox host
Using Quotas Inside Containers
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Quotas allow to set limits inside a container for the amount of disk
-space that each user can use. This only works on ext4 image based
-storage types and currently does not work with unprivileged
-containers.
+Quotas allow to set limits inside a container for the amount of disk space that
+each user can use.
-Activating the `quota` option causes the following mount options to be
-used for a mount point:
+NOTE: This currently requires the use of legacy 'cgroups'.
+
+NOTE: This only works on ext4 image based storage types and currently only
+works with privileged containers.
+
+Activating the `quota` option causes the following mount options to be used for
+a mount point:
`usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0`
-This allows quotas to be used like you would on any other system. You
-can initialize the `/aquota.user` and `/aquota.group` files by running
+This allows quotas to be used like on any other system. You can initialize the
+`/aquota.user` and `/aquota.group` files by running:
----
-quotacheck -cmug /
-quotaon /
+# quotacheck -cmug /
+# quotaon /
----
-and edit the quotas via the `edquota` command. Refer to the documentation
-of the distribution running inside the container for details.
+Then edit the quotas using the `edquota` command. Refer to the documentation of
+the distribution running inside the container for details.
-NOTE: You need to run the above commands for every mount point by passing
-the mount point's path instead of just `/`.
+NOTE: You need to run the above commands for every mount point by passing the
+mount point's path instead of just `/`.
Using ACLs Inside Containers
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The standard Posix **A**ccess **C**ontrol **L**ists are also available inside containers.
-ACLs allow you to set more detailed file ownership than the traditional user/
-group/others model.
+The standard Posix **A**ccess **C**ontrol **L**ists are also available inside
+containers. ACLs allow you to set more detailed file ownership than the
+traditional user/group/others model.
-Container Network
------------------
+Backup of Container mount points
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-You can configure up to 10 network interfaces for a single
-container. The corresponding options are called `net0` to `net9`, and
-they can contain the following setting:
+To include a mount point in backups, enable the `backup` option for it in the
+container configuration. For an existing mount point `mp0`
-include::pct-network-opts.adoc[]
+----
+mp0: guests:subvol-100-disk-1,mp=/root/files,size=8G
+----
+
+add `backup=1` to enable it.
+
+----
+mp0: guests:subvol-100-disk-1,mp=/root/files,size=8G,backup=1
+----
+
+NOTE: When creating a new mount point in the GUI, this option is enabled by
+default.
+
+To disable backups for a mount point, add `backup=0` in the way described
+above, or uncheck the *Backup* checkbox on the GUI.
+
+Replication of Containers mount points
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+By default, additional mount points are replicated when the Root Disk is
+replicated. If you want the {pve} storage replication mechanism to skip a mount
+point, you can set the *Skip replication* option for that mount point.
+As of {pve} 5.0, replication requires a storage of type `zfspool`. Adding a
+mount point to a different type of storage when the container has replication
+configured requires to have *Skip replication* enabled for that mount point.
Backup and Restore
Container Backup
~~~~~~~~~~~~~~~~
-It is possible to use the `vzdump` tool for container backup. Please
-refer to the `vzdump` manual page for details.
+It is possible to use the `vzdump` tool for container backup. Please refer to
+the `vzdump` manual page for details.
Restoring Container Backups
~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Restoring container backups made with `vzdump` is possible using the
-`pct restore` command. By default, `pct restore` will attempt to restore as much
-of the backed up container configuration as possible. It is possible to override
-the backed up configuration by manually setting container options on the command
-line (see the `pct` manual page for details).
+Restoring container backups made with `vzdump` is possible using the `pct
+restore` command. By default, `pct restore` will attempt to restore as much of
+the backed up container configuration as possible. It is possible to override
+the backed up configuration by manually setting container options on the
+command line (see the `pct` manual page for details).
NOTE: `pvesm extractconfig` can be used to view the backed up configuration
contained in a vzdump archive.
``Simple'' Restore Mode
^^^^^^^^^^^^^^^^^^^^^^^
-If neither the `rootfs` parameter nor any of the optional `mpX` parameters
-are explicitly set, the mount point configuration from the backed up
-configuration file is restored using the following steps:
+If neither the `rootfs` parameter nor any of the optional `mpX` parameters are
+explicitly set, the mount point configuration from the backed up configuration
+file is restored using the following steps:
. Extract mount points and their options from backup
-. Create volumes for storage backed mount points (on storage provided with the
-`storage` parameter, or default local storage if unset)
+. Create volumes for storage backed mount points on the storage provided with
+ the `storage` parameter (default: `local`).
. Extract files from backup archive
-. Add bind and device mount points to restored configuration (limited to root user)
+. Add bind and device mount points to restored configuration (limited to root
+ user)
NOTE: Since bind and device mount points are never backed up, no files are
restored in the last step, but only the configuration options. The assumption
By setting the `rootfs` parameter (and optionally, any combination of `mpX`
parameters), the `pct restore` command is automatically switched into an
advanced mode. This advanced mode completely ignores the `rootfs` and `mpX`
-configuration options contained in the backup archive, and instead only
-uses the options explicitly provided as parameters.
+configuration options contained in the backup archive, and instead only uses
+the options explicitly provided as parameters.
-This mode allows flexible configuration of mount point settings at restore time,
-for example:
+This mode allows flexible configuration of mount point settings at restore
+time, for example:
* Set target storages, volume sizes and other options for each mount point
-individually
+ individually
* Redistribute backed up files according to new mount point scheme
* Restore to device and/or bind mount points (limited to root user)
Managing Containers with `pct`
------------------------------
-`pct` is the tool to manage Linux Containers on {pve}. You can create
-and destroy containers, and control execution (start, stop, migrate,
-...). You can use pct to set parameters in the associated config file,
-like network configuration or memory limits.
-
+The ``Proxmox Container Toolkit'' (`pct`) is the command-line tool to manage
+{pve} containers. It enables you to create or destroy containers, as well as
+control the container execution (start, stop, reboot, migrate, etc.). It can be
+used to set parameters in the config file of a container, for example the
+network configuration or memory limits.
CLI Usage Examples
~~~~~~~~~~~~~~~~~~
-Create a container based on a Debian template (provided you have
-already downloaded the template via the web interface)
+Create a container based on a Debian template (provided you have already
+downloaded the template via the web interface)
- pct create 100 /var/lib/vz/template/cache/debian-8.0-standard_8.0-1_amd64.tar.gz
+----
+# pct create 100 /var/lib/vz/template/cache/debian-10.0-standard_10.0-1_amd64.tar.gz
+----
Start container 100
- pct start 100
+----
+# pct start 100
+----
Start a login session via getty
- pct console 100
+----
+# pct console 100
+----
Enter the LXC namespace and run a shell as root user
- pct enter 100
+----
+# pct enter 100
+----
Display the configuration
- pct config 100
+----
+# pct config 100
+----
-Add a network interface called `eth0`, bridged to the host bridge `vmbr0`,
-set the address and gateway, while it's running
+Add a network interface called `eth0`, bridged to the host bridge `vmbr0`, set
+the address and gateway, while it's running
- pct set 100 -net0 name=eth0,bridge=vmbr0,ip=192.168.15.147/24,gw=192.168.15.1
+----
+# pct set 100 -net0 name=eth0,bridge=vmbr0,ip=192.168.15.147/24,gw=192.168.15.1
+----
Reduce the memory of the container to 512MB
- pct set 100 -memory 512
+----
+# pct set 100 -memory 512
+----
+Destroying a container always removes it from Access Control Lists and it always
+removes the firewall configuration of the container. You have to activate
+'--purge', if you want to additionally remove the container from replication jobs,
+backup jobs and HA resource configurations.
-Files
-------
+----
+# pct destroy 100 --purge
+----
-`/etc/pve/lxc/<CTID>.conf`::
+Move a mount point volume to a different storage.
-Configuration file for the container '<CTID>'.
+----
+# pct move-volume 100 mp0 other-storage
+----
+Reassign a volume to a different CT. This will remove the volume `mp0` from
+the source CT and attaches it as `mp1` to the target CT. In the background
+the volume is being renamed so that the name matches the new owner.
-Container Advantages
---------------------
+----
+# pct move-volume 100 mp0 --target-vmid 200 --target-volume mp1
+----
-* Simple, and fully integrated into {pve}. Setup looks similar to a normal
- VM setup.
-** Storage (ZFS, LVM, NFS, Ceph, ...)
+Obtaining Debugging Logs
+~~~~~~~~~~~~~~~~~~~~~~~~
-** Network
+In case `pct start` is unable to start a specific container, it might be
+helpful to collect debugging output by passing the `--debug` flag (replace `CTID` with
+the container's CTID):
-** Authentication
+----
+# pct start CTID --debug
+----
-** Cluster
+Alternatively, you can use the following `lxc-start` command, which will save
+the debug log to the file specified by the `-o` output option:
-* Fast: minimal overhead, as fast as bare metal
+----
+# lxc-start -n CTID -F -l DEBUG -o /tmp/lxc-CTID.log
+----
-* High density (perfect for idle workloads)
+This command will attempt to start the container in foreground mode, to stop
+the container run `pct shutdown CTID` or `pct stop CTID` in a second terminal.
-* REST API
+The collected debug log is written to `/tmp/lxc-CTID.log`.
-* Direct hardware access
+NOTE: If you have changed the container's configuration since the last start
+attempt with `pct start`, you need to run `pct start` at least once to also
+update the configuration used by `lxc-start`.
+[[pct_migration]]
+Migration
+---------
-Technology Overview
--------------------
+If you have a cluster, you can migrate your Containers with
+
+----
+# pct migrate <ctid> <target>
+----
+
+This works as long as your Container is offline. If it has local volumes or
+mount points defined, the migration will copy the content over the network to
+the target host if the same storage is defined there.
+
+Running containers cannot live-migrated due to technical limitations. You can
+do a restart migration, which shuts down, moves and then starts a container
+again on the target node. As containers are very lightweight, this results
+normally only in a downtime of some hundreds of milliseconds.
+
+A restart migration can be done through the web interface or by using the
+`--restart` flag with the `pct migrate` command.
+
+A restart migration will shut down the Container and kill it after the
+specified timeout (the default is 180 seconds). Then it will migrate the
+Container like an offline migration and when finished, it starts the Container
+on the target node.
+
+[[pct_configuration]]
+Configuration
+-------------
-- Integrated into {pve} graphical user interface (GUI)
+The `/etc/pve/lxc/<CTID>.conf` file stores container configuration, where
+`<CTID>` is the numeric ID of the given container. Like all other files stored
+inside `/etc/pve/`, they get automatically replicated to all other cluster
+nodes.
-- LXC (https://linuxcontainers.org/)
+NOTE: CTIDs < 100 are reserved for internal purposes, and CTIDs need to be
+unique cluster wide.
-- cgmanager for cgroup management
+.Example Container Configuration
+----
+ostype: debian
+arch: amd64
+hostname: www
+memory: 512
+swap: 512
+net0: bridge=vmbr0,hwaddr=66:64:66:64:64:36,ip=dhcp,name=eth0,type=veth
+rootfs: local:107/vm-107-disk-1.raw,size=7G
+----
-- lxcfs to provive containerized /proc file system
+The configuration files are simple text files. You can edit them using a normal
+text editor, for example, `vi` or `nano`.
+This is sometimes useful to do small corrections, but keep in mind that you
+need to restart the container to apply such changes.
-- apparmor
+For that reason, it is usually better to use the `pct` command to generate and
+modify those files, or do the whole thing using the GUI.
+Our toolkit is smart enough to instantaneously apply most changes to running
+containers. This feature is called ``hot plug'', and there is no need to restart
+the container in that case.
-- CRIU: for live migration (planned)
+In cases where a change cannot be hot-plugged, it will be registered as a
+pending change (shown in red color in the GUI).
+They will only be applied after rebooting the container.
-- We use latest available kernels (4.4.X)
-- Image based deployment (templates)
+File Format
+~~~~~~~~~~~
-- Container setup from host (Network, DNS, Storage, ...)
+The container configuration file uses a simple colon separated key/value
+format. Each line has the following format:
+-----
+# this is a comment
+OPTION: value
+-----
-ifdef::manvolnum[]
-include::pve-copyright.adoc[]
-endif::manvolnum[]
+Blank lines in those files are ignored, and lines starting with a `#` character
+are treated as comments and are also ignored.
+
+It is possible to add low-level, LXC style configuration directly, for example:
+
+----
+lxc.init_cmd: /sbin/my_own_init
+----
+or
+
+----
+lxc.init_cmd = /sbin/my_own_init
+----
+
+The settings are passed directly to the LXC low-level tools.
+
+
+[[pct_snapshots]]
+Snapshots
+~~~~~~~~~
+
+When you create a snapshot, `pct` stores the configuration at snapshot time
+into a separate snapshot section within the same configuration file. For
+example, after creating a snapshot called ``testsnapshot'', your configuration
+file will look like this:
+
+.Container configuration with snapshot
+----
+memory: 512
+swap: 512
+parent: testsnaphot
+...
+
+[testsnaphot]
+memory: 512
+swap: 512
+snaptime: 1457170803
+...
+----
+
+There are a few snapshot related properties like `parent` and `snaptime`. The
+`parent` property is used to store the parent/child relationship between
+snapshots. `snaptime` is the snapshot creation time stamp (Unix epoch).
+
+
+[[pct_options]]
+Options
+~~~~~~~
+include::pct.conf.5-opts.adoc[]
+
+
+Locks
+-----
+Container migrations, snapshots and backups (`vzdump`) set a lock to prevent
+incompatible concurrent actions on the affected container. Sometimes you need
+to remove such a lock manually (e.g., after a power failure).
+----
+# pct unlock <CTID>
+----
+CAUTION: Only do this if you are sure the action which set the lock is no
+longer running.
+ifdef::manvolnum[]
+
+Files
+------
+
+`/etc/pve/lxc/<CTID>.conf`::
+
+Configuration file for the container '<CTID>'.
+
+
+include::pve-copyright.adoc[]
+endif::manvolnum[]
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