Lexi

Lexi is a Linux Containers assistant for LXD and LXC 2.0+ (including 3.x), designed to make interacting with containers faster and easier for developers.

It enables different container configs to be stored locally per-project (in git repos for example). This means project-specific configs can be easily shared across teams.

It also wraps the standard CLI for LXC, greatly simplifying common commands and providing a few enhancements and additions.

See Usage section below for more details.

Setting up LXD/LXC

Lexi is intended to be used with an up-to-date installation of LXD and LXC. The recommended installation is via snapd. If you have previously installed an older version of LXC (< 2.0) it's best to completely remove it first, then install LXD.

Some installation instructions for LXD are here: https://linuxcontainers.org/lxd/getting-started-cli/ \

TLDR version:

$ sudo apt install snap # install snap
$ sudo snap install lxd # install LXD (includes LXC)
$ sudo lxd init # runs the wizard for initial LXD setup; hit enter for defaults
$ sudo usermod -aG lxd $USER # Add current user to lxd group
$ su - $USER # Pick up groups changes for current user (or log out and back in)

Searchable LXD docs are here: https://lxd.readthedocs.io/en/latest/

Lexi Setup

Dependencies

Lexi requires jq, a small library for parsing json.
Install with: $ sudo apt install jq

Setup

• Clone this repo and run $ sudo make install
• Copy the example /.lexi directory into any project and edit the YAML files to taste
• Run $ lexi setup to create the network bridge used by lexi. This should only be needed once.

Shared directories

Lexi uses shiftfs for managing user mappings on directories shared between the host and the container.

This requires a recent Linux kernel on the host (5+) which is present in Ubuntu 18 and above.

To check if you have shiftfs enabled, do: $ modinfo shiftfs.

To enable shiftfs with LXD (snap version), do:

$ sudo snap set lxd shiftfs.enable=true
$ sudo systemctl reload snap.lxd.daemon

For more info on shiftfs see this post.

Config Files

See local config README

Usage

Lexi provides an alternative CLI for lxc. All lexi commands are based on the standard lxc interface, with the following adjustments and extras:

Quick Commands

Instead of having to remember the specific image you use in the current project, or constantly having to remember and re-type the container name in each command, lexi pulls these from your local configs and handles it for you.

So for example, this command:

$ lxc launch <arbitrary-container-name> <specific-image>:<specific-version> -p <manually-created-profile>

becomes this:

$ lexi launch

The same pattern above is applied to all common lxc commands, such as start,stop,delete, info, etc...

Nice Fallbacks

lexi also adds some helpful automated additions, for example;

If you run $ lexi start but the container hasn't been created yet, it will launch and start it automatically instead of just throwing a "not found" error and forcing you manually retype the commands to launch it.

$ lexi delete will use the --force flag by default, instead of throwing an error if the container is running and forcing you to manually retype the command with --force.

New Commands

lexi ssh

If you're using an image that supports cloud-init (such as ubuntu:18.04), lexi will add your public SSH key to the container on launch, and provides the following command (which will directly connect via SSH to the container):

$ lexi ssh

This will connect using the default_user defined in your configs, but can take a second argument to override the default, eg:

$ lexi ssh root

lexi login

To get a simpler shell in the container (without SSH) you can use:

$ lexi login

As with the lexi ssh (above), this logs in as the default_user defined in the local configs, but can be overridden by passing a specific user as the second argument.

lexi recreate

$ lexi recreate

The above command will force-delete the current container and re-launch a fresh instance.

Snapshot Management

Snaphot management can be done with the following (adjusted/added) commands:

• lexi snapshot
• lexi snapshot-delete
• lexi snapshot-restore or lexi restore

As before, the basic snapshot command will default to creating snaphots named snap0, snap1, snap2 etc if no name is supplied as the second argument.

The snapshot-delete and snapshot-restore (or restore) commands will default to using the most recent snapshot, or can take a snapshot name as second argument, eg:

$ lexi snapshot-restore example-snapshot

You can list available snapshots for the current container with $ lexi snapshot-list, or see the full info for the current container (including snapshots) with $ lexi info.

Bash Completion

If you have bash completion enabled, Lexi implements tab-completion for all of it's commands, so if you type $ lexi snapshot and hit <tab><tab>, you'll see:

$ lexi snapshot
snapshot    snapshot-list   shapshot-delete     snapshot-restore 

Static IPs

Defining a static local IP means that (for example) entries for the container can be easily added to Ansible projects. See the local config README for more details.

Standard Interface

The standard lxc commands are untouched and can still be used as normal for any complex operations, like editing network configurations.

Acknowledgements

Inspired partly by devenv and partly by the ease-of-use of old Virtual Machine software like Vagrant.