LXD¶

LXD is a next generation system container and virtual machine manager. It offers a unified user experience around full Linux systems running inside containers or virtual machines.

It’s image based with pre-made images available for a wide number of Linux distributions and is built around a very powerful, yet pretty simple, REST API.

To get a better idea of what LXD is and what it does, you can try it online! Then if you want to run it locally, take a look at our getting started guide.

Release announcements can be found here: https://linuxcontainers.org/lxd/news/

And the release tarballs here: https://linuxcontainers.org/lxd/downloads/

The documentation is here: https://linuxcontainers.org/lxd/docs/master/

Status¶

Type	Service	Status
CI (client)	GitHub
CI (server)	Jenkins
Go documentation	Godoc
Static analysis	GoReport
Translations	Weblate
Project status	CII Best Practices

Installing LXD from packages¶

The LXD daemon only works on Linux but the client tool (lxc) is available on most platforms.

OS	Format	Command
Linux	Snap	snap install lxd
Windows	Chocolatey	choco install lxc
MacOS	Homebrew	brew install lxc

More instructions on installing LXD for a wide variety of Linux distributions and operating systems can be found on our website.

Installing LXD from source¶

We recommend having the latest versions of liblxc (>= 3.0.0 required) available for LXD development. Additionally, LXD requires Golang 1.13 or later to work. On ubuntu, you can get those with:

sudo apt update
sudo apt install acl attr autoconf dnsmasq-base git golang libacl1-dev libcap-dev liblxc1 liblxc-dev libsqlite3-dev libtool libudev-dev liblz4-dev libuv1-dev make pkg-config rsync squashfs-tools tar tcl xz-utils ebtables

Note that when building LXC yourself, ensure to build it with the appropriate security related libraries installed which our testsuite tests. Again, on ubuntu, you can get those with:

sudo apt install libapparmor-dev libseccomp-dev libcap-dev

There are a few storage backends for LXD besides the default “directory” backend. Installing these tools adds a bit to initramfs and may slow down your host boot, but are needed if you’d like to use a particular backend:

sudo apt install lvm2 thin-provisioning-tools
sudo apt install btrfs-progs

To run the testsuite, you’ll also need:

sudo apt install curl gettext jq sqlite3 uuid-runtime socat

From Source: Building the latest version¶

These instructions for building from source are suitable for individual developers who want to build the latest version of LXD, or build a specific release of LXD which may not be offered by their Linux distribution. Source builds for integration into Linux distributions are not covered here and may be covered in detail in a separate document in the future.

git clone https://github.com/lxc/lxd
cd lxd

This will download the current development tree of LXD and place you in the source tree. Then proceed to the instructions below to actually build and install LXD.

From Source: Building a Release¶

The LXD release tarballs bundle a complete dependency tree as well as a local copy of libraft and libdqlite for LXD’s database setup.

tar zxvf lxd-4.18.tar.gz
cd lxd-4.18

This will unpack the release tarball and place you inside of the source tree. Then proceed to the instructions below to actually build and install LXD.

Starting the Build¶

The actual building is done by two separate invocations of the Makefile: make deps – which builds libraries required by LXD – and make, which builds LXD itself. At the end of make deps, a message will be displayed which will specify environment variables that should be set prior to invoking make. As new versions of LXD are released, these environment variable settings may change, so be sure to use the ones displayed at the end of the make deps process, as the ones below (shown for example purposes) may not exactly match what your version of LXD requires:

We recommend having at least 2GB of RAM to allow the build to complete.

make deps
# Follow the instructions from `make deps` to export the required environment variables.
# For example:
#  export CGO_CFLAGS="${CGO_CFLAGS} -I$(go env GOPATH)/deps/dqlite/include/ -I$(go env GOPATH)/deps/raft/include/"
#  export CGO_LDFLAGS="${CGO_LDFLAGS} -L$(go env GOPATH)/deps/dqlite/.libs/ -L$(go env GOPATH)/deps/raft/.libs/"
#  export LD_LIBRARY_PATH="$(go env GOPATH)/deps/dqlite/.libs/:$(go env GOPATH)/deps/raft/.libs/:${LD_LIBRARY_PATH}"
#  export CGO_LDFLAGS_ALLOW="(-Wl,-wrap,pthread_create)|(-Wl,-z,now)"
make

From Source: Installing¶

Once the build completes, you simply keep the source tree, add the directory referenced by $(go env GOPATH)/bin to your shell path, and set the LD_LIBRARY_PATH variable printed by make deps to your environment. This might look something like this for a ~/.bashrc file:

export PATH="${PATH}:$(go env GOPATH)/bin"
export LD_LIBRARY_PATH="$(go env GOPATH)/deps/dqlite/.libs/:$(go env GOPATH)/deps/raft/.libs/:${LD_LIBRARY_PATH}"

Now, the lxd and lxc binaries will be available to you and can be used to set up LXD. The binaries will automatically find and use the dependencies built in $(go env GOPATH)/deps thanks to the LD_LIBRARY_PATH environment variable.

Machine Setup¶

You’ll 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

Now you can run the daemon (the --group sudo bit allows everyone in the sudo group to talk to LXD; you can create your own group if you want):

sudo -E PATH=${PATH} LD_LIBRARY_PATH=${LD_LIBRARY_PATH} $(go env GOPATH)/bin/lxd --group sudo

Security¶

LXD, similar to other container and VM managers provides a UNIX socket for local communication.

WARNING: Anyone with access to that socket can fully control LXD, which includes the ability to attach host devices and filesystems, this should therefore only be given to users who would be trusted with root access to the host.

When listening on the network, the same API is available on a TLS socket (HTTPS), specific access on the remote API can be restricted through Canonical RBAC.

More details are available here.

Getting started with LXD¶

Now that you have LXD running on your system you can read the getting started guide or go through more examples and configurations in our documentation.

Bug reports¶

Bug reports and Feature requests can be filed at: https://github.com/lxc/lxd/issues/new

Contributing¶

Fixes and new features are greatly appreciated but please read our contributing guidelines first.

Support and discussions¶

Forum¶

A discussion forum is available at: https://discuss.linuxcontainers.org

Mailing-lists¶

We use the LXC mailing-lists for developer and user discussions, you can find and subscribe to those at: https://lists.linuxcontainers.org

IRC¶

If you prefer live discussions, you can find us in #lxc on irc.libera.chat.

FAQ¶

How to enable LXD server for remote access?¶

By default LXD server is not accessible from the networks as it only listens on a local unix socket. You can make LXD available from the network by specifying additional addresses to listen to. This is done with the core.https_address config variable.

To see the current server configuration, run:

lxc config show

To set the address to listen to, find out what addresses are available and use the config set command on the server:

ip addr
lxc config set core.https_address 192.168.1.15

When I do a `lxc remote add` over https, it asks for a password?¶

By default, LXD has no password for security reasons, so you can’t do a remote add this way. In order to set a password, do:

lxc config set core.trust_password SECRET

on the host LXD is running on. This will set the remote password that you can then use to do lxc remote add.

You can also access the server without setting a password by copying the client certificate from .config/lxc/client.crt to the server and adding it with:

lxc config trust add client.crt

How do I configure LXD storage?¶

LXD supports btrfs, ceph, directory, lvm and zfs based storage.

First make sure you have the relevant tools for your filesystem of choice installed on the machine (btrfs-progs, lvm2 or zfsutils-linux).

By default, LXD comes with no configured network or storage. You can get a basic configuration done with:

lxd init

lxd init supports both directory based storage and ZFS. If you want something else, you’ll need to use the lxc storage command:

lxc storage create default BACKEND [OPTIONS...]
lxc profile device add default root disk path=/ pool=default

BACKEND is one of btrfs, ceph, dir, lvm or zfs.

Unless specified otherwise, LXD will setup loop based storage with a sane default size.

For production environments, you should be using block backed storage instead both for performance and reliability reasons.

How can I live migrate a container using LXD?¶

Live migration requires a tool installed on both hosts called CRIU, which is available in Ubuntu via:

sudo apt install criu

Then, launch your container with the following,

lxc launch ubuntu SOME-NAME
sleep 5s # let the container get to an interesting state
lxc move host1:SOME-NAME host2:SOME-NAME

And with luck you’ll have migrated the container :). Migration is still in experimental stages and may not work for all workloads. Please report bugs on lxc-devel, and we can escalate to CRIU lists as necessary.

Can I bind mount my home directory in a container?¶

Yes. This can be done using a disk device:

lxc config device add container-name home disk source=/home/${USER} path=/home/ubuntu

For unprivileged containers, you will also need one of:

Pass shift=true to the lxc config device add call. This depends on shiftfs being supported (see lxc info)
raw.idmap entry (see Idmaps for user namespace)
Recursive POSIX ACLs placed on your home directory

Either of those can be used to allow the user in the container to have working read/write permissions. When not setting one of those, everything will show up as the overflow uid/gid (65536:65536) and access to anything that’s not world readable will fail.

Privileged containers do not have this issue as all uid/gid inthe container are the same outside. But that’s also the cause of most of the security issues with such privileged containers.

How can I run docker inside a LXD container?¶

In order to run Docker inside a LXD container the security.nesting property of the container should be set to true.

lxc config set <container> security.nesting true

Note that LXD containers cannot load kernel modules, so depending on your Docker configuration you may need to have the needed extra kernel modules loaded by the host.

You can do so by setting a comma separate list of kernel modules that your container needs with:

lxc config set <container> linux.kernel_modules <modules>

We have also received some reports that creating a /.dockerenv file in your container can help Docker ignore some errors it’s getting due to running in a nested environment.

Hacking on LXD¶

Directly using the REST API¶

The LXD REST API can be used locally via unauthenticated Unix socket or remotely via SSL encapsulated TCP.

Via Unix socket¶

curl --unix-socket /var/lib/lxd/unix.socket \
    -H "Content-Type: application/json" \
    -X POST \
    -d @hello-ubuntu.json \
    lxd/1.0/containers

or for snap users:

curl --unix-socket /var/snap/lxd/common/lxd/unix.socket \
    -H "Content-Type: application/json" \
    -X POST \
    -d @hello-ubuntu.json \
    lxd/1.0/containers

Via TCP¶

TCP requires some additional configuration and is not enabled by default.

lxc config set core.https_address "[::]:8443"

curl -k -L \
    --cert ~/.config/lxc/client.crt \
    --key ~/.config/lxc/client.key \
    -H "Content-Type: application/json" \
    -X POST \
    -d @hello-ubuntu.json \
    "https://127.0.0.1:8443/1.0/containers"

JSON payload¶

The hello-ubuntu.json file referenced above could contain something like:

{
    "name":"some-ubuntu",
    "ephemeral":true,
    "config":{
        "limits.cpu":"2"
    },
    "source": {
        "type":"image",
        "mode":"pull",
        "protocol":"simplestreams",
        "server":"https://cloud-images.ubuntu.com/releases",
        "alias":"18.04"
    }
}