X-Git-Url: https://git.proxmox.com/?p=pve-docs.git;a=blobdiff_plain;f=pct.adoc;h=925294e94f7b3aa90faf6711497b6d05c7930d3f;hp=e21f8840fc03e94130dccff002ad861ffd7cf13b;hb=105bc8f1e6fbb7ca1f3c49b082f8da70a8a153a5;hpb=4a2ae9edf7bb23c1f0588566c9e01016e73c2f12 diff --git a/pct.adoc b/pct.adoc index e21f884..925294e 100644 --- a/pct.adoc +++ b/pct.adoc @@ -59,8 +59,8 @@ 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 micro-containers with docker, it is best to -run them inside a VM. +NOTE: If you want to run micro-containers (with docker, rct, ...), it +is best to run them inside a VM. Security Considerations @@ -98,14 +98,171 @@ kernel security bug rather than a LXC issue. LXC people think unprivileged containers are safe by design. +Configuration +------------- + +The '/etc/pve/lxc/.conf' files stores container configuration, +where '' is the numeric ID of the given container. Note that +CTIDs < 100 are reserved for internal purposes, and CTIDs need to be +cluster wide unique. Files are stored inside '/etc/pve/', so they get +automatically replicated to all other cluster nodes. + +.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. + +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. + +File Format +~~~~~~~~~~~ + +Container configuration files use a simple colon separated key/value +format. Each line has the following format: + + # this is a comment + OPTION: value + +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 + +Those settings are directly passed to the LXC low-level tools. + +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 view snapshot related properties like 'parent' and +'snaptime'. They 'parent' property is used to store the parent/child +relationship between snapshots. 'snaptime' is the snapshot creation +time stamp (unix epoch). + +Guest Operating System Configuration +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +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: + +set /etc/hostname:: to set the container name + +modify /etc/hosts:: allow to lookup the local hostname + +network setup:: pass the complete network setup to the container + +configure DNS:: pass information about DNS servers + +adopt the init system:: for example, fix the number os 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 same time on all containers + +Above task depends on the OS type, so the implementation is different +for each OS type. You can also disable any modifications by manually +setting the 'ostype' to 'unmanaged'. + +OS type detection is done by testing for certain files inside the +container: + +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 + +NOTE: Container start fails is configured 'ostype' differs from auto +detected type. + +Container Storage +----------------- + +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 turend +out to be complex and error prone, so we trie 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'. And it enables us +to use advanced storage features like snapshots and clones. 'vzdump' +can also use the snapshots 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 provides an easy way to share data between different containers. + + Managing Containers with 'pct' ------------------------------ -'pct' is a tool to manages Linux Containers (LXC). You can create and -destroy containers, and control execution -(start/stop/suspend/resume). Besides that, you can use pct to set -parameters in the associated config file, like network configuration -or memory. +'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. CLI Usage Examples ------------------ @@ -143,9 +300,9 @@ Reduce the memory of the container to 512MB Files ------ -'/etc/pve/lxc/.conf':: +'/etc/pve/lxc/.conf':: -Configuration file for the container +Configuration file for the container ''. Container Advantages