LXD

LXD is a container "hypervisor" and a new user experience for Linux Containers.

Related articles

• Linux Containers

Setup

Required software

Install LXC and the lxd^AUR package, then start lxd.service.

See Linux Containers#Enable support to run unprivileged containers (optional) if you want to run unprivileged containers. Otherwise see #Launching container without CONFIG_USER_NS.

Alternative installation method

An alternative method of installation is via snapd, by installing the snapd^AUR package and running:

# snap install lxd

Configure LXD

LXD needs to configure a storage pool, and (if you want internet access) network configuration. To do so, run the following as root:

# lxd init

Accessing LXD as a unprivileged user

By default the LXD daemon allows users in the lxd group access, so add your user to the group:

# usermod -a -G lxd <user>

Basic usage

Create container

LXD has two parts, the daemon (the lxd binary), and the client (the lxc binary). Now that the daemon is all configured and running, you can create a container:

$ lxc launch ubuntu:16.04

Alternatively, you can also use a remote LXD host as a source of images. One comes pre-configured in LXD, called "images" (images.linuxcontainers.org)

$ lxc launch images:centos/7/amd64 centos

Advance usage

LXD Networking

LXD uses LXC's networking capabilities. By default it connects containers to the lxcbr0 network device. Refer to the LXC documentation on network configuration to set up a bridge for your containers.

If you want to use a different interface than lxcbr0 edit the default using the lxc command line tool:

$ lxc profile edit default

An editor will open with a config file that by default contains:

name: default
config: {}
devices:
  eth0:
    name: eth0
    nictype: bridged
    parent: lxcbr0
    type: nic

You can set the parent parameter to whichever bridge you want LXD to attach the containers to by default.

Example network configuration

Thanks to @jpic, the LXD package now provides some example networking configuration in /usr/share/lxd/. To use this configuration run the following commands:

$ ln -s /usr/share/lxd/dnsmasq-lxd.conf /etc/dnsmasq-lxd.conf
$ ln -s /usr/share/lxd/systemd/system/dnsmasq@lxd.service /etc/systemd/system/dnsmasq@lxd.service 
$ ln -s /usr/share/lxd/netctl/lxd  /etc/netctl/lxd
$ ln -s /usr/share/lxd/dbus-1/system.d/dnsmasq-lxd.conf /etc/dbus-1/system.d/dnsmasq-lxd.conf

If you use NetworkManager, also symlink the following file:

$ ln -s /usr/share/lxd/NetworkManager/dnsmasq.d/lxd.conf /etc/NetworkManager/dnsmasq.d/lxd.conf

Change parent: lxcbr0 to parent: lxd:

$ lxc profile edit default

Finally, enable and start dnsmasq@lxd.service and netctl@lxd.service.

If you encounter issue with the provided example configuration, or have suggestions to improve it, please leave a comment on the lxd^AUR page.

Modify processes and files limit

You may want to increase file descriptor limit or max user processes limit, since default file descriptor limit is 1024 on Arch Linux.

Edit the lxd.service:

# systemctl edit lxd.service

[Service]
LimitNOFILE=infinity
LimitNPROC=infinity
TasksMax=infinity

Troubleshooting

Check kernel config

By default Arch Linux kernel is compiled correctly for Linux Containers and its frontend LXD. However, if you're using a custom kernel, or changed kernel options the kernel might be configured incorrectly. Verify that the running kernel is properly configured to run a container:

$ lxc-checkconfig

Launching container without CONFIG_USER_NS

For launching images you must provide security.privileged=true during image creation:

$ lxc launch ubuntu:16.04 ubuntu -c security.privileged=true

Or for already existed image you may edit config:

$ lxc config edit ubuntu

name: ubuntu
profiles:
- default
config:
  ...
  security.privileged: "true"
  ...
devices:
  root:
    path: /
    type: disk
ephemeral: false

Or to enable security.privileged=true for new containers, edit the config for the default profile:

$ lxc profile edit default

No ipv4 on unprivileged Arch container

This was tested and validated on LXD v.2.20. The container can not start the systemd-networkd service so does not get a valid ipv4 address. A work-around was suggested by Stéphane Graber (Github Issue), execute on the host and restart the container:

$ lxc profile set default security.syscalls.blacklist "keyctl errno 38"

stgraber: "The reason is that the networkd systemd unit somehow makes use of the kernel keyring, which doesn't work inside unprivileged containers right now. The line above makes that system call return not-implemented which is enough of a workaround to get things going again."

Resource limits are not applied when viewed from inside a container

The service lxcfs (found in the Community repository) needs to be installed and started :

$ systemctl start lxcfs

lxd will need to be restarted. Enable lxcfs for the service to be started at boot time.

See also

• Official documentation
• The official LXD homepage
• The LXD GitHub page