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' files stores container configuration,
105 where '<CTID>' is the numeric ID of the given container. Note that
106 CTIDs < 100 are reserved for internal purposes, and CTIDs need to be
107 unique cluster wide. Files are stored inside '/etc/pve/', so they get
108 automatically replicated to all other cluster nodes.
110 .Example Container Configuration
117 net0: bridge=vmbr0,hwaddr=66:64:66:64:64:36,ip=dhcp,name=eth0,type=veth
118 rootfs: local:107/vm-107-disk-1.raw,size=7G
121 Those configuration files are simple text files, and you can edit them
122 using a normal text editor ('vi', 'nano', ...). This is sometimes
123 useful to do small corrections, but keep in mind that you need to
124 restart the container to apply such changes.
126 For that reason, it is usually better to use the 'pct' command to
127 generate and modify those files, or do the whole thing using the GUI.
128 Our toolkit is smart enough to instantaneously apply most changes to
129 running containers. This feature is called "hot plug", and there is no
130 need to restart the container in that case.
135 Container configuration files use a simple colon separated key/value
136 format. Each line has the following format:
141 Blank lines in those files are ignored, and lines starting with a '#'
142 character are treated as comments and are also ignored.
144 It is possible to add low-level, LXC style configuration directly, for
147 lxc.init_cmd: /sbin/my_own_init
151 lxc.init_cmd = /sbin/my_own_init
153 Those settings are directly passed to the LXC low-level tools.
158 When you create a snapshot, 'pct' stores the configuration at snapshot
159 time into a separate snapshot section within the same configuration
160 file. For example, after creating a snapshot called 'testsnapshot',
161 your configuration file will look like this:
163 .Container Configuration with Snapshot
177 There are a few snapshot related properties like 'parent' and
178 'snaptime'. The 'parent' property is used to store the parent/child
179 relationship between snapshots. 'snaptime' is the snapshot creation
180 time stamp (unix epoch).
182 Guest Operating System Configuration
183 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
185 We normally try to detect the operating system type inside the
186 container, and then modify some files inside the container to make
187 them work as expected. Here is a short list of things we do at
190 set /etc/hostname:: to set the container name
192 modify /etc/hosts:: to allow lookup of the local hostname
194 network setup:: pass the complete network setup to the container
196 configure DNS:: pass information about DNS servers
198 adapt the init system:: for example, fix the number of spawned getty processes
200 set the root password:: when creating a new container
202 rewrite ssh_host_keys:: so that each container has unique keys
204 randomize crontab:: so that cron does not start at the same time on all containers
206 The above task depends on the OS type, so the implementation is different
207 for each OS type. You can also disable any modifications by manually
208 setting the 'ostype' to 'unmanaged'.
210 OS type detection is done by testing for certain files inside the
213 Ubuntu:: inspect /etc/lsb-release ('DISTRIB_ID=Ubuntu')
215 Debian:: test /etc/debian_version
217 Fedora:: test /etc/fedora-release
219 RedHat or CentOS:: test /etc/redhat-release
221 ArchLinux:: test /etc/arch-release
223 Alpine:: test /etc/alpine-release
225 NOTE: Container start fails if the configured 'ostype' differs from the auto
232 Container Images, sometimes also referred to as "templates" or
233 "appliances", are 'tar' archives which contain everything to run a
234 container. You can think of it as a tidy container backup. Like most
235 modern container toolkits, 'pct' uses those images when you create a
236 new container, for example:
238 pct create 999 local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz
240 Proxmox itself ships a set of basic templates for most common
241 operating systems, and you can download them using the 'pveam' (short
242 for {pve} Appliance Manager) command line utility. You can also
243 download https://www.turnkeylinux.org/[TurnKey Linux] containers using
244 that tool (or the graphical user interface).
246 Our image repositories contain a list of available images, and there
247 is a cron job run each day to download that list. You can trigger that
248 update manually with:
252 After that you can view the list of available images using:
256 You can restrict this large list by specifying the 'section' you are
257 interested in, for example basic 'system' images:
259 .List available system images
261 # pveam available --section system
262 system archlinux-base_2015-24-29-1_x86_64.tar.gz
263 system centos-7-default_20160205_amd64.tar.xz
264 system debian-6.0-standard_6.0-7_amd64.tar.gz
265 system debian-7.0-standard_7.0-3_amd64.tar.gz
266 system debian-8.0-standard_8.0-1_amd64.tar.gz
267 system ubuntu-12.04-standard_12.04-1_amd64.tar.gz
268 system ubuntu-14.04-standard_14.04-1_amd64.tar.gz
269 system ubuntu-15.04-standard_15.04-1_amd64.tar.gz
270 system ubuntu-15.10-standard_15.10-1_amd64.tar.gz
273 Before you can use such a template, you need to download them into one
274 of your storages. You can simply use storage 'local' for that
275 purpose. For clustered installations, it is preferred to use a shared
276 storage so that all nodes can access those images.
278 pveam download local debian-8.0-standard_8.0-1_amd64.tar.gz
280 You are now ready to create containers using that image, and you can
281 list all downloaded images on storage 'local' with:
285 local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz 190.20MB
288 The above command shows you the full {pve} volume identifiers. They include
289 the storage name, and most other {pve} commands can use them. For
290 examply you can delete that image later with:
292 pveam remove local:vztmpl/debian-8.0-standard_8.0-1_amd64.tar.gz
298 Traditional containers use a very simple storage model, only allowing
299 a single mount point, the root file system. This was further
300 restricted to specific file system types like 'ext4' and 'nfs'.
301 Additional mounts are often done by user provided scripts. This turend
302 out to be complex and error prone, so we try to avoid that now.
304 Our new LXC based container model is more flexible regarding
305 storage. First, you can have more than a single mount point. This
306 allows you to choose a suitable storage for each application. For
307 example, you can use a relatively slow (and thus cheap) storage for
308 the container root file system. Then you can use a second mount point
309 to mount a very fast, distributed storage for your database
312 The second big improvement is that you can use any storage type
313 supported by the {pve} storage library. That means that you can store
314 your containers on local 'lvmthin' or 'zfs', shared 'iSCSI' storage,
315 or even on distributed storage systems like 'ceph'. It also enables us
316 to use advanced storage features like snapshots and clones. 'vzdump'
317 can also use the snapshot feature to provide consistent container
320 Last but not least, you can also mount local devices directly, or
321 mount local directories using bind mounts. That way you can access
322 local storage inside containers with zero overhead. Such bind mounts
323 also provide an easy way to share data between different containers.
326 Managing Containers with 'pct'
327 ------------------------------
329 'pct' is the tool to manage Linux Containers on {pve}. You can create
330 and destroy containers, and control execution (start, stop, migrate,
331 ...). You can use pct to set parameters in the associated config file,
332 like network configuration or memory limits.
337 Create a container based on a Debian template (provided you have
338 already downloaded the template via the webgui)
340 pct create 100 /var/lib/vz/template/cache/debian-8.0-standard_8.0-1_amd64.tar.gz
346 Start a login session via getty
350 Enter the LXC namespace and run a shell as root user
354 Display the configuration
358 Add a network interface called eth0, bridged to the host bridge vmbr0,
359 set the address and gateway, while it's running
361 pct set 100 -net0 name=eth0,bridge=vmbr0,ip=192.168.15.147/24,gw=192.168.15.1
363 Reduce the memory of the container to 512MB
365 pct set -memory 512 100
370 '/etc/pve/lxc/<CTID>.conf'::
372 Configuration file for the container '<CTID>'.
378 - Simple, and fully integrated into {pve}. Setup looks similar to a normal
381 * Storage (ZFS, LVM, NFS, Ceph, ...)
389 - Fast: minimal overhead, as fast as bare metal
391 - High density (perfect for idle workloads)
395 - Direct hardware access
401 - Integrated into {pve} graphical user interface (GUI)
403 - LXC (https://linuxcontainers.org/)
405 - cgmanager for cgroup management
407 - lxcfs to provive containerized /proc file system
411 - CRIU: for live migration (planned)
413 - We use latest available kernels (4.2.X)
415 - Image based deployment (templates)
417 - Container setup from host (Network, DNS, Storage, ...)
421 include::pve-copyright.adoc[]