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 Free BSD or MS Windows inside.
42 * For security reasons, access to host resources need to be
43 restricted. This is done with AppArmor, SecComp filters and other
44 kernel feature. 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 to difficult to use those tools
50 directly. Instead, we provide a small wrapper called `pct`, the
51 "Proxmox Container Toolkit".
53 The toolkit it 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 VM provides 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 a LXC issue. LXC people think
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. 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 Those configuration files are simple text files, and you can edit them
111 using a normal text editor ('vi', 'nano', ...). This is sometimes
112 useful to do small corrections, but keep in mind that you need to
113 restart the container to apply such changes.
115 For that reason, it is usually better to use the 'pct' command to
116 generate and modify those files, or do the whole thing using the GUI.
117 Our toolkit is smart enough to instantaneously apply most changes to
118 running containers (hot plug).
124 Container configuration files use a simple colon separated key/value
125 format. Each line has the following format:
130 Blank lines in those files are ignored, and lines starting with a '#'
131 character are treated as comments and are also ignored.
133 It is possible to add low-level, LXC style configuration directly, for
136 lxc.init_cmd: /sbin/my_own_init
140 lxc.init_cmd = /sbin/my_own_init
142 Those settings are directly passed to the LXC low-level tools.
145 Guest Operating System Configuration
146 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
148 We normally try to detect the operating system type inside the
149 container, and then modify some files inside the container to make
150 them work as expected. Here is a short list of things we do at
153 set /etc/hostname:: to set the container name
155 modify /etc/hosts:: allow to lookup the local hostname
157 network setup:: pass the complete network setup to the container
159 configure DNS:: pass information about DNS servers
161 adopt the init system:: for example, fix the number os spawned getty processes
163 set the root password:: when creating a new container
165 rewrite ssh_host_keys:: so that each container has unique keys
167 randomize crontab:: so that cron does not start at same time on all containers
169 Above task depends on the OS type, so the implementation is different
170 for each OS type. You can also disable any modifications by manually
171 setting the 'ostype' to 'unmanaged'.
173 OS type detection is done by testing for certain files inside the
176 Ubuntu:: inspect /etc/lsb-release ('DISTRIB_ID=Ubuntu')
178 Debian:: test /etc/debian_version
180 Fedora:: test /etc/fedora-release
182 RedHat or CentOS:: test /etc/redhat-release
184 ArchLinux:: test /etc/arch-release
186 Alpine:: test /etc/alpine-release
188 NOTE: Container start fails is configured 'ostype' differs from auto
194 Traditional containers use a very simple storage model, only allowing
195 a single mount point, the root file system. This was further
196 restricted to specific file system types like 'ext4' and 'nfs'.
197 Additional mounts are often done by user provided scripts. This turend
198 out to be complex and error prone, so we trie to avoid that now.
200 Our new LXC based container model is more flexible regarding
201 storage. First, you can have more than a single mount point. This
202 allows you to choose a suitable storage for each application. For
203 example, you can use a relatively slow (and thus cheap) storage for
204 the container root file system. Then you can use a second mount point
205 to mount a very fast, distributed storage for your database
208 The second big improvement is that you can use any storage type
209 supported by the {pve} storage library. That means that you can store
210 your containers on local 'lvmthin' or 'zfs', shared 'iSCSI' storage,
211 or even on distributed storage systems like 'ceph'. And it enables us
212 to use advanced storage features like snapshots and clones. 'vzdump'
213 can also use the snapshots feature to provide consistent container
216 Last but not least, you can also mount local devices directly, or
217 mount local directories using bind mounts. That way you can access
218 local storage inside containers with zero overhead. Such bind mounts
219 also provides an easy way to share data between different containers.
222 Managing Containers with 'pct'
223 ------------------------------
225 'pct' is the tool to manage Linux Containers on {pve}. You can create
226 and destroy containers, and control execution (start, stop, migrate,
227 ...). You can use pct to set parameters in the associated config file,
228 like network configuration or memory.
233 Create a container based on a Debian template (provided you downloaded
234 the template via the webgui before)
236 pct create 100 /var/lib/vz/template/cache/debian-8.0-standard_8.0-1_amd64.tar.gz
242 Start a login session via getty
246 Enter the LXC namespace and run a shell as root user
250 Display the configuration
254 Add a network interface called eth0, bridged to the host bridge vmbr0,
255 set the address and gateway, while it's running
257 pct set 100 -net0 name=eth0,bridge=vmbr0,ip=192.168.15.147/24,gw=192.168.15.1
259 Reduce the memory of the container to 512MB
261 pct set -memory 512 100
266 '/etc/pve/lxc/<CTID>.conf'::
268 Configuration file for the container '<CTID>'.
274 - Simple, and fully integrated into {pve}. Setup looks similar to a normal
277 * Storage (ZFS, LVM, NFS, Ceph, ...)
285 - Fast: minimal overhead, as fast as bare metal
287 - High density (perfect for idle workloads)
291 - Direct hardware access
297 - Integrated into {pve} graphical user interface (GUI)
299 - LXC (https://linuxcontainers.org/)
301 - cgmanager for cgroup management
303 - lxcfs to provive containerized /proc file system
307 - CRIU: for live migration (planned)
309 - We use latest available kernels (4.2.X)
311 - image based deployment (templates)
313 - Container setup from host (Network, DNS, Storage, ...)
317 include::pve-copyright.adoc[]