ifdef::manvolnum[] PVE({manvolnum}) ================ include::attributes.txt[] NAME ---- pct - Tool to manage Linux Containers (LXC) on Proxmox VE SYNOPSYS -------- include::pct.1-synopsis.adoc[] DESCRIPTION ----------- endif::manvolnum[] ifndef::manvolnum[] Proxmox Container Toolkit ========================= include::attributes.txt[] endif::manvolnum[] 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. 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: * You can only run Linux based OS inside containers, i.e. it is not possible to run Free BSD or MS Windows inside. * For security reasons, access to host resources need to be restricted. This is done with AppArmor, SecComp filters and other kernel feature. Be prepared that some syscalls are not allowed inside containers. {pve} uses https://linuxcontainers.org/[LXC] as underlying container technology. We consider LXC as low-level library, which provides countless options. It would be to difficult to use those tools directly. Instead, we provide a small wrapper called `pct`, the "Proxmox Container Toolkit". The toolkit it 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 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, rct, ...), it is best to run them inside a VM. 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 VM provides better isolation. 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: Privileged containers ~~~~~~~~~~~~~~~~~~~~~ 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. Unprivileged containers ~~~~~~~~~~~~~~~~~~~~~~~ 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 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. CTIDs need to be unique - cluster wide. Files are stored inside '/etc/pve/', so they get automatically replicated to all other cluster nodes. Those configuration files are simple text files, and you can edit them using a normal text editor ('vi', 'nano', ...). But one can also use the 'pct' command to generate and modify those files, or do the whole thing using the GUI. 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. 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 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 ------------------ Create a container based on a Debian template (provided you downloaded the template via the webgui before) pct create 100 /var/lib/vz/template/cache/debian-8.0-standard_8.0-1_amd64.tar.gz Start container 100 pct start 100 Start a login session via getty pct console 100 Enter the LXC namespace and run a shell as root user pct enter 100 Display the configuration pct config 100 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 Reduce the memory of the container to 512MB pct set -memory 512 100 Files ------ '/etc/pve/lxc/.conf':: Configuration file for the container ''. Container Advantages -------------------- - Simple, and fully integrated into {pve}. Setup looks similar to a normal VM setup. * Storage (ZFS, LVM, NFS, Ceph, ...) * Network * Authentification * Cluster - Fast: minimal overhead, as fast as bare metal - High density (perfect for idle workloads) - REST API - Direct hardware access Technology Overview ------------------- - Integrated into {pve} graphical user interface (GUI) - LXC (https://linuxcontainers.org/) - cgmanager for cgroup management - lxcfs to provive containerized /proc file system - apparmor - CRIU: for live migration (planned) - We use latest available kernels (4.2.X) - image based deployment (templates) - Container setup from host (Network, DNS, Storage, ...) ifdef::manvolnum[] include::pve-copyright.adoc[] endif::manvolnum[]