LXD
LXD is a container "hypervisor" and a new user experience for Linux Containers.
Setup
Required software
Install LXC and the lxdAUR package, then start lxd.service
.
Verify that the running kernel is properly configured to run a container:
$ lxc-checkconfig
The safest type of container that LXD can create is unprivileged. This is done by leveraging the Linux kernel's User Namespaces feature. However, due to more general security concerns, the default Arch kernel does not ship with User Namespaces enabled (CONFIG_USER_NS
is a kernel compile-time decision). You have three (3) options to use a kernel with CONFIG_USER_NS
and thereby create unprivileged containers:
- Install the linux-hardened kernel package along-side the default linux kernel. When you wish to run unprivileged LXD containers, boot with linux-hardened by selecting it in the bootloader. linux-hardened is compiled with
CONFIG_USER_NS
. Otherwise, run with linux as normal. - Install the linux-usernsAUR or linux-lts-usernsAUR packages from the AUR. Both are compiled with
CONFIG_USER_NS
, the latter being the Long-Term Support version. - Compile and install your own custom kernel with
CONFIG_USER_NS
enabled.
Sub{u,g}id configuration
You will need sub{u,g}ids for root, so that LXD can create the unprivileged containers:
$ echo "root:1000000:65536" | sudo tee -a /etc/subuid /etc/subgid
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>
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 lxdAUR page.
Basic usage
First steps
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:14.04
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
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 Archlinux
$ sudo systemctl edit lxd
And config as follow:
[Service] LimitNOFILE=infinity LimitNPROC=infinity TasksMax=infinity
Then restart lxd
$ sudo systemctl restart lxd
Troubleshooting
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."