4 include::attributes.txt[]
9 pct - Tool to manage Linux Containers (LXC) on Proxmox VE
15 include::pct.1-synopsis.adoc[]
22 Proxmox Container Toolkit
23 =========================
24 include::attributes.txt[]
28 Containers are a lightweight alternative to fully virtualized
29 VMs. Instead of emulating a complete Operating System (OS), containers
30 simply use the OS of the host they run on. This implies that all
31 containers use the same kernel, and that they can access resources
32 from the host directly.
34 This is great because containers do not waste CPU power nor memory due
35 to kernel emulation. Container run-time costs are close to zero and
36 usually negligible. But there are also some drawbacks you need to
39 * You can only run Linux based OS inside containers, i.e. it is not
40 possible to run FreeBSD or MS Windows inside.
42 * For security reasons, access to host resources needs to be
43 restricted. This is done with AppArmor, SecComp filters and other
44 kernel features. Be prepared that some syscalls are not allowed
47 {pve} uses https://linuxcontainers.org/[LXC] as underlying container
48 technology. We consider LXC as low-level library, which provides
49 countless options. It would be too difficult to use those tools
50 directly. Instead, we provide a small wrapper called `pct`, the
51 "Proxmox Container Toolkit".
53 The toolkit is tightly coupled with {pve}. That means that it is aware
54 of the cluster setup, and it can use the same network and storage
55 resources as fully virtualized VMs. You can even use the {pve}
56 firewall, or manage containers using the HA framework.
58 Our primary goal is to offer an environment as one would get from a
59 VM, but without the additional overhead. We call this "System
62 NOTE: If you want to run micro-containers (with docker, rct, ...), it
63 is best to run them inside a VM.
66 Security Considerations
67 -----------------------
69 Containers use the same kernel as the host, so there is a big attack
70 surface for malicious users. You should consider this fact if you
71 provide containers to totally untrusted people. In general, fully
72 virtualized VMs provide better isolation.
74 The good news is that LXC uses many kernel security features like
75 AppArmor, CGroups and PID and user namespaces, which makes containers
76 usage quite secure. We distinguish two types of containers:
81 Security is done by dropping capabilities, using mandatory access
82 control (AppArmor), SecComp filters and namespaces. The LXC team
83 considers this kind of container as unsafe, and they will not consider
84 new container escape exploits to be security issues worthy of a CVE
85 and quick fix. So you should use this kind of containers only inside a
86 trusted environment, or when no untrusted task is running as root in
89 Unprivileged containers
90 ~~~~~~~~~~~~~~~~~~~~~~~
92 This kind of containers use a new kernel feature called user
93 namespaces. The root uid 0 inside the container is mapped to an
94 unprivileged user outside the container. This means that most security
95 issues (container escape, resource abuse, ...) in those containers
96 will affect a random unprivileged user, and so would be a generic
97 kernel security bug rather than an LXC issue. The LXC team thinks
98 unprivileged containers are safe by design.
104 The '/etc/pve/lxc/<CTID>.conf' file stores container configuration,
105 where '<CTID>' is the numeric ID of the given container. Like all
106 other files stored inside '/etc/pve/', they get automatically
107 replicated to all other cluster nodes.
109 NOTE: CTIDs < 100 are reserved for internal purposes, and CTIDs need to be
112 .Example Container Configuration
119 net0: bridge=vmbr0,hwaddr=66:64:66:64:64:36,ip=dhcp,name=eth0,type=veth
120 rootfs: local:107/vm-107-disk-1.raw,size=7G
123 Those configuration files are simple text files, and you can edit them
124 using a normal text editor ('vi', 'nano', ...). This is sometimes
125 useful to do small corrections, but keep in mind that you need to
126 restart the container to apply such changes.
128 For that reason, it is usually better to use the 'pct' command to
129 generate and modify those files, or do the whole thing using the GUI.
130 Our toolkit is smart enough to instantaneously apply most changes to
131 running containers. This feature is called "hot plug", and there is no
132 need to restart the container in that case.
137 Container configuration files use a simple colon separated key/value
138 format. Each line has the following format:
143 Blank lines in those files are ignored, and lines starting with a '#'
144 character are treated as comments and are also ignored.
146 It is possible to add low-level, LXC style configuration directly, for
149 lxc.init_cmd: /sbin/my_own_init
153 lxc.init_cmd = /sbin/my_own_init
155 Those settings are directly passed to the LXC low-level tools.
160 When you create a snapshot, 'pct' stores the configuration at snapshot
161 time into a separate snapshot section within the same configuration
162 file. For example, after creating a snapshot called 'testsnapshot',
163 your configuration file will look like this:
165 .Container Configuration with Snapshot
179 There are a few snapshot related properties like 'parent' and
180 'snaptime'. The 'parent' property is used to store the parent/child
181 relationship between snapshots. 'snaptime' is the snapshot creation
182 time stamp (unix epoch).
184 Guest Operating System Configuration
185 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
187 We normally try to detect the operating system type inside the
188 container, and then modify some files inside the container to make
189 them work as expected. Here is a short list of things we do at
192 set /etc/hostname:: to set the container name
194 modify /etc/hosts:: to allow lookup of the local hostname
196 network setup:: pass the complete network setup to the container
198 configure DNS:: pass information about DNS servers
200 adapt the init system:: for example, fix the number of spawned getty processes
202 set the root password:: when creating a new container
204 rewrite ssh_host_keys:: so that each container has unique keys
206 randomize crontab:: so that cron does not start at the same time on all containers
208 The above task depends on the OS type, so the implementation is different
209 for each OS type. You can also disable any modifications by manually
210 setting the 'ostype' to 'unmanaged'.
212 OS type detection is done by testing for certain files inside the
215 Ubuntu:: inspect /etc/lsb-release ('DISTRIB_ID=Ubuntu')
217 Debian:: test /etc/debian_version
219 Fedora:: test /etc/fedora-release
221 RedHat or CentOS:: test /etc/redhat-release
223 ArchLinux:: test /etc/arch-release
225 Alpine:: test /etc/alpine-release
227 NOTE: Container start fails if the configured 'ostype' differs from the auto
234 Container Images, sometimes also referred to as "templates" or
235 "appliances", are 'tar' archives which contain everything to run a
236 container. You can think of it as a tidy container backup. Like most
237 modern container toolkits, 'pct' uses those images when you create a
238 new container, for example:
240 pct create 999 local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz
242 Proxmox itself ships a set of basic templates for most common
243 operating systems, and you can download them using the 'pveam' (short
244 for {pve} Appliance Manager) command line utility. You can also
245 download https://www.turnkeylinux.org/[TurnKey Linux] containers using
246 that tool (or the graphical user interface).
248 Our image repositories contain a list of available images, and there
249 is a cron job run each day to download that list. You can trigger that
250 update manually with:
254 After that you can view the list of available images using:
258 You can restrict this large list by specifying the 'section' you are
259 interested in, for example basic 'system' images:
261 .List available system images
263 # pveam available --section system
264 system archlinux-base_2015-24-29-1_x86_64.tar.gz
265 system centos-7-default_20160205_amd64.tar.xz
266 system debian-6.0-standard_6.0-7_amd64.tar.gz
267 system debian-7.0-standard_7.0-3_amd64.tar.gz
268 system debian-8.0-standard_8.0-1_amd64.tar.gz
269 system ubuntu-12.04-standard_12.04-1_amd64.tar.gz
270 system ubuntu-14.04-standard_14.04-1_amd64.tar.gz
271 system ubuntu-15.04-standard_15.04-1_amd64.tar.gz
272 system ubuntu-15.10-standard_15.10-1_amd64.tar.gz
275 Before you can use such a template, you need to download them into one
276 of your storages. You can simply use storage 'local' for that
277 purpose. For clustered installations, it is preferred to use a shared
278 storage so that all nodes can access those images.
280 pveam download local debian-8.0-standard_8.0-1_amd64.tar.gz
282 You are now ready to create containers using that image, and you can
283 list all downloaded images on storage 'local' with:
287 local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz 190.20MB
290 The above command shows you the full {pve} volume identifiers. They include
291 the storage name, and most other {pve} commands can use them. For
292 examply you can delete that image later with:
294 pveam remove local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz
300 Traditional containers use a very simple storage model, only allowing
301 a single mount point, the root file system. This was further
302 restricted to specific file system types like 'ext4' and 'nfs'.
303 Additional mounts are often done by user provided scripts. This turend
304 out to be complex and error prone, so we try to avoid that now.
306 Our new LXC based container model is more flexible regarding
307 storage. First, you can have more than a single mount point. This
308 allows you to choose a suitable storage for each application. For
309 example, you can use a relatively slow (and thus cheap) storage for
310 the container root file system. Then you can use a second mount point
311 to mount a very fast, distributed storage for your database
314 The second big improvement is that you can use any storage type
315 supported by the {pve} storage library. That means that you can store
316 your containers on local 'lvmthin' or 'zfs', shared 'iSCSI' storage,
317 or even on distributed storage systems like 'ceph'. It also enables us
318 to use advanced storage features like snapshots and clones. 'vzdump'
319 can also use the snapshot feature to provide consistent container
322 Last but not least, you can also mount local devices directly, or
323 mount local directories using bind mounts. That way you can access
324 local storage inside containers with zero overhead. Such bind mounts
325 also provide an easy way to share data between different containers.
328 Managing Containers with 'pct'
329 ------------------------------
331 'pct' is the tool to manage Linux Containers on {pve}. You can create
332 and destroy containers, and control execution (start, stop, migrate,
333 ...). You can use pct to set parameters in the associated config file,
334 like network configuration or memory limits.
339 Create a container based on a Debian template (provided you have
340 already downloaded the template via the webgui)
342 pct create 100 /var/lib/vz/template/cache/debian-8.0-standard_8.0-1_amd64.tar.gz
348 Start a login session via getty
352 Enter the LXC namespace and run a shell as root user
356 Display the configuration
360 Add a network interface called eth0, bridged to the host bridge vmbr0,
361 set the address and gateway, while it's running
363 pct set 100 -net0 name=eth0,bridge=vmbr0,ip=192.168.15.147/24,gw=192.168.15.1
365 Reduce the memory of the container to 512MB
367 pct set -memory 512 100
372 '/etc/pve/lxc/<CTID>.conf'::
374 Configuration file for the container '<CTID>'.
377 Container Mountpoints
378 ---------------------
380 Beside the root directory the container can also have additional mountpoints.
381 Currently there are basically three types of mountpoints: storage backed
382 mountpoints, bind mounts and device mounts.
384 Storage backed mountpoints are managed by the {pve} storage subsystem and come
385 in three different flavors:
387 - Image based: These are raw images containing a single ext4 formatted file
389 - ZFS Subvolumes: These are technically bind mounts, but with managed storage,
390 and thus allow resizing and snapshotting.
391 - Directories: passing `size=0` triggers a special case where instead of a raw
392 image a directory is created.
394 Bind mounts are considered to not be managed by the storage subsystem, so you
395 cannot make snapshots or deal with quotas from inside the container, and with
396 unprivileged containers you might run into permission problems caused by the
397 user mapping, and cannot use ACLs from inside an unprivileged container.
399 Similarly device mounts are not managed by the storage, but for these the
400 `quota` and `acl` options will be honored.
402 WARNING: Because of existing issues in the Linux kernel's freezer
403 subsystem the usage of FUSE mounts inside a container is strongly
404 advised against, as containers need to be frozen for suspend or
405 snapshot mode backups. If FUSE mounts cannot be replaced by other
406 mounting mechanisms or storage technologies, it is possible to
407 establish the FUSE mount on the Proxmox host and use a bind
408 mountpoint to make it accessible inside the container.
410 Using quotas inside containers
411 ------------------------------
413 Quotas allow to set limits inside a container for the amount of disk space
414 that each user can use.
415 This only works on ext4 image based storage types and currently does not work
416 with unprivileged containers.
418 Activating the `quota` option causes the following mount options to be used for
419 a mountpoint: `usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0`
421 This allows quotas to be used like you would on any other system. You can
422 initialize the `/aquota.user` and `/aquota.group` files by running
427 and edit the quotas via the `edquota` command. Refer to the documentation
428 of the distribution running inside the container for details.
430 NOTE: You need to run the above commands for every mountpoint by passing
431 the mountpoint's path instead of just `/`.
433 Using ACLs inside containers
434 ----------------------------
436 The standard Posix Access Control Lists are also available inside containers.
437 ACLs allow you to set more detailed file ownership than the traditional user/
443 - Simple, and fully integrated into {pve}. Setup looks similar to a normal
446 * Storage (ZFS, LVM, NFS, Ceph, ...)
454 - Fast: minimal overhead, as fast as bare metal
456 - High density (perfect for idle workloads)
460 - Direct hardware access
466 - Integrated into {pve} graphical user interface (GUI)
468 - LXC (https://linuxcontainers.org/)
470 - cgmanager for cgroup management
472 - lxcfs to provive containerized /proc file system
476 - CRIU: for live migration (planned)
478 - We use latest available kernels (4.2.X)
480 - Image based deployment (templates)
482 - Container setup from host (Network, DNS, Storage, ...)
486 include::pve-copyright.adoc[]