Additional LXD resources
This page offers more in-depth information on LXD itself. To learn how to set up LXD with Juju see Using LXD with Juju.
The topics presented here are:
- LXD and images
- Non-admin user credentials
- Useful LXD client commands
- Using the LXD snap
- LXD logs
- Further LXD help and reading
LXD and images
LXD is image based: all LXD containers come from images and any LXD daemon instance (also called a "remote") can serve images. When LXD is installed a locally-running remote is provided (Unix domain socket) and the client is configured to talk to it (named 'local'). The client is also configured to talk to several other, non-local, ones (named 'ubuntu', 'ubuntu-daily', and 'images').
An image is identified by its fingerprint (SHA-256 hash), and can be tagged with multiple aliases.
For any image-related command, an image is specified by its alias or by its fingerprint. Both are shown in image lists. An image's filename is its full fingerprint while an image list displays its partial fingerprint. Either type of fingerprint can be used to refer to images.
Juju pulls official cloud images from the 'ubuntu' remote
(http://cloud-images.ubuntu.com) and creates the necessary alias. Any
subsequent requests will be satisfied by the LXD cache (/var/lib/lxd/images
).
Cached images can be seen with lxc image list
.
Image cache expiration and image synchronization mechanisms are built-in.
Non-admin user credentials
To grant a regular user access to a LXD-based controller a certificate credential is required. This certificate is generated and shared with the user who will then use it as a credential. See Creating users for details on adding users, registering them, and granting them permissions.
On the LXD host generate the certificate with the autoload-credentials
command. Use the below sample session as a guide:
Looking for cloud and credential information locally... 1. LXD credential "localhost" (new) Select a credential to save by number, or type Q to quit: 1 Select the cloud it belongs to, or type Q to quit []: localhost Saved LXD credential "localhost" to cloud localhost 1. LXD credential "localhost" (existing, will overwrite) Select a credential to save by number, or type Q to quit: Q
A certificate credential will have been created. Export it to a file, say
localhost-credentials.yaml
, by typing the following:
juju credentials localhost --format=yaml > localhost-credentials.yaml
Now transfer the file to the user that requires access to the cloud. Once done, on that user's system, the credential can be added:
juju add-credential localhost -f localhost-credentials.yaml
See Cloud credentials for more details on how credentials are used.
Useful LXD client commands
There are many client commands available. Some common ones, including those covered above, are given below.
client commands | meaning |
---|---|
lxc launch |
creates an LXD container |
lxc list |
lists all LXD containers |
lxc delete |
deletes an LXD container |
lxc remote list |
lists remotes |
lxc info |
displays status of localhost |
lxc info <container> |
displays status of container |
lxc config show <container> |
displays configuration of container |
lxc image info <alias or fingerprint> |
displays status of image |
lxc exec <container> <executable> |
runs program on container |
lxc exec <container> /bin/bash |
spawns shell on container |
lxc file pull <container></path/to/file> . |
copies file from container |
lxc file push </path/to/file> <container>/ |
copies file to container |
lxc stop <container> |
stops container |
lxc image alias delete <alias> |
deletes image alias |
lxc image alias create <alias> <fingerprint> |
creates image alias |
Using the LXD snap
The LXD project will soon be moving from the APT installation method (Debian package) to installing via a snap. Some users may want to opt in early, before building their infrastructure, as moving to the snap entails a migration of containers. The LXD snap is very well tested (as is the included migration tool).
First ensure that snapd
is installed:
sudo apt install snapd
Important: On Ubuntu 14.04 LTS (Trusty), installing snapd
will bring in a new kernel (4.4.0 series) as a dependency. You will then need to reboot. Attempting to install a snap without doing so will result in failure.
Now install the LXD snap:
sudo snap install lxd
If LXD is already installed via APT and there are no existing containers under the current installation then simply remove the software:
sudo apt purge liblxc1 lxcfs lxd lxd-client
If containers do exist under the old system the lxd.migrate
utility should be
used to migrate them to the new system. Once the migration is complete, you
will be prompted to have the old software removed.
Start the migration tool by running:
sudo lxd.migrate
LXD logs
LXD itself logs to /var/log/lxd/lxd.log
and Juju machines created via the LXD
local provider log to /var/log/lxd/juju-UUID-machine-ID
. However, the
standard way to view logs is with the debug-log
command (see the
Juju logs page for details).
Note: For LXD snap users, the log directory is located at /var/snap/lxd/common/lxd/logs
.
Further help and reading
See lxc --help
for more information on LXD client usage and lxd --help
for
assistance with the daemon. See upstream documentation for
LXD configuration.