Introduction
Intro to go here explaining LXD versus LXC and why you want to use it. For now, key bullets,
- LXD sits on top of LXC
- API to orchestrates containers locally and remotely
- Allows moving and copying between hosts
- Takes advantage of advanced file systems (in particular ZFS)
You should finish the LXC and LXC with Advanced Networking before starting this article.
Setup
A key feature of virtualization technology is taking snapshots. With traditional file systems, this is expensive in terms of storage and speed. Next generation ZFS solves many of theses problems and it is recommended by Ubuntu to install and use with LXD,
sudo apt install zfsutils-linux # must be using Ubuntu 16.04 or higher.
Next configure LXD,
sudo lxd init
...
Images
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Cached Images in Image Store
List images currently cached in the image store. There should be none to start,
lxc image list
Image Servers
LXD has 3 image server lists by default,
Image Server LIst | Purpose | Comment |
---|---|---|
ubuntu: | Ubuntu stable images. | We'll be working with this one. |
ubuntu-daily: | ||
images: | All Linux distributions. | For example you can load a RedHat Linux alternative distrobution. |
Pulling Image Server Lists
Let's look at the ubuntu: list,
lxc image list ubuntu: | less +--------------------+--------------+--------+-------------------------------------------------+---------+----------+-------------------------------+ | ALIAS | FINGERPRINT | PUBLIC | DESCRIPTION | ARCH | SIZE | UPLOAD DATE | +--------------------+--------------+--------+-------------------------------------------------+---------+----------+-------------------------------+ | p (5 more) | 6041c5e200b6 | yes | ubuntu 12.04 LTS amd64 (release) (20161205) | x86_64 | 156.47MB | Dec 5, 2016 at 12:00am (UTC) | +--------------------+--------------+--------+-------------------------------------------------+---------+----------+-------------------------------+ | p/armhf (2 more) | c19b1fff3336 | yes | ubuntu 12.04 LTS armhf (release) (20161205) | armv7l | 135.19MB | Dec 5, 2016 at 12:00am (UTC) | +--------------------+--------------+--------+-------------------------------------------------+---------+----------+-------------------------------+ | p/i386 (2 more) | ce5c6821eebb | yes | ubuntu 12.04 LTS i386 (release) (20161205) | i686 | 139.28MB | Dec 5, 2016 at 12:00am (UTC) | +--------------------+--------------+--------+-------------------------------------------------+---------+----------+-------------------------------+ ...
The output table from list is not very clear. I don't understand what to reference to use the "launch" command. Will put explanation here once figured out. Here is what I can tell,
Example "launch" Command Reference | Column | Note |
---|---|---|
ubuntu:16.04 | This will download from the Ubuntu image server grabbing the latest 16.04 matching your machines architecture, win my case amd64. | |
ubuntu:6041c5e200b6 | FINGERPRINT | Will specifically reference the specific image in the list. |
images:centos/7 | Go against the "images" image server, download the latest cantos version 7 matching your machines architecture. | |
images:centos/6/amd64 | In this example, specifies latest version 6 and specifies the architecture. |
At this point LXD is all setup and ready to use.
Spinning Up an LXD Container
Creating and starting a container can be done with one command,
lxc launch ubuntu:16.04 container01
This command does the following simultaneously,
- References the ubuntu: Image Server List
- Looks for 16.01 images
- Matches the current architecture of the machine you are on (in my example
- Checks the cache Image Store for the required image
- Download (if not in Image Store) the target image
- Setup Container called container01 with default settings
- Install the target image into container01
- Start container01
Replace launch with init if you would like the container to not start by itself.
We can see the downloaded target image,
lxc image list +-------+--------------+--------+---------------------------------------------+--------+----------+------------------------------+ | ALIAS | FINGERPRINT | PUBLIC | DESCRIPTION | ARCH | SIZE | UPLOAD DATE | +-------+--------------+--------+---------------------------------------------+--------+----------+------------------------------+ | | f4c9feb3e401 | no | ubuntu 16.04 LTS amd64 (release) (20161205) | x86_64 | 143.53MB | Dec 22, 2016 at 3:37am (UTC) | +-------+--------------+--------+---------------------------------------------+--------+----------+------------------------------+
Now instead of empty, we see the downloaded image which matches our architecture.
Also, let's look at the running container. The commands are only slightly different than using straight LXC,
lxc list +-------------+---------+----------------------+------+------------+-----------+ | NAME | STATE | IPV4 | IPV6 | TYPE | SNAPSHOTS | +-------------+---------+----------------------+------+------------+-----------+ | container01 | RUNNING | 10.94.217.171 (eth0) | | PERSISTENT | 0 | +-------------+---------+----------------------+------+------------+-----------+ # Inspect the container, lxc info container01 Name: container01 Remote: unix:/var/lib/lxd/unix.socket Architecture: x86_64 Created: 2016/12/22 03:37 UTC Status: Running Type: persistent Profiles: default Pid: 19681 Ips: eth0: inet 10.94.217.171 vethDXUYOE eth0: inet6 fe80::216:3eff:fe07:69ea vethDXUYOE lo: inet 127.0.0.1 lo: inet6 ::1 Resources: Processes: 26 Disk usage: root: 144.32MB Memory usage: Memory (current): 23.24MB Memory (peak): 45.28MB # ...
For illustration of flexiblity and preparing for the next section, we will update and setup Apache inside of container01.
Remotely execute update of the container from the host which are run as root,
lxc exec container01 apt-get update lxc exec container01 apt-get dist-upgrade
And now we'll actually create a bash to simulate going in as a console. Notice the prompt change indicating you are root inside of container01,
lxc exec container01 bash root@container01:~#
Now we install Apache and then exit back to our host,
apt install apache2 exit # Takes you back to your host.
Managing Containers Between Hosts
The most compelling reason to use LXD is ability to transport between containers. Setup a second LXD host on the same network. In this example we end up with two hosts,
Host | Containers | Comment |
---|---|---|
myhost01 | Where we setup container01 with Apache running inside. | This will be the host we can to copy the container from also called remote host. |
myhost02 | Just empty at the moment. | This will be the client also called the local machine. |
Expose Remote Host
In order for the local machine to connect, the remote host needs to be setup to be exposed on the network with a password. Following the instructions here, that work has been done while initializing LXD.
Configure Local Machine
myhost02 (local machine) needs to be made aware of the remote host. I suppose there are multiple ways of doing this and interested in if there is automatic discovery. For now, I'm going to use direct IP address.
lxc remote add myhost01 192.168.0.109 Certificate fingerprint: 7344c171bdc30a20e215e536a7959353b55ab6243a019819fb62385fa02d26b2 ok (y/n)? y Admin password for myhost01: Client certificate stored at server: myhost01
Now the list has been updated to have myhost02 as an entry,
lxc remote list +-----------------+------------------------------------------+---------------+--------+--------+ | NAME | URL | PROTOCOL | PUBLIC | STATIC | +-----------------+------------------------------------------+---------------+--------+--------+ | images | https://images.linuxcontainers.org | simplestreams | YES | NO | +-----------------+------------------------------------------+---------------+--------+--------+ | local (default) | unix:// | lxd | NO | YES | +-----------------+------------------------------------------+---------------+--------+--------+ | myhost01 | https://192.168.0.109:8443 | lxd | NO | NO | +-----------------+------------------------------------------+---------------+--------+--------+ | ubuntu | https://cloud-images.ubuntu.com/releases | simplestreams | YES | YES | +-----------------+------------------------------------------+---------------+--------+--------+ | ubuntu-daily | https://cloud-images.ubuntu.com/daily | simplestreams | YES | YES | +-----------------+------------------------------------------+---------------+--------+--------+
Interacting with Remote Host
Interaction is exactly the same as a local container except you specify the registered lxd host name,
lxc list myhost01: # Notice myhost01 has container01 which we had setup. +-------------+---------+----------------------+------+------------+-----------+ | NAME | STATE | IPV4 | IPV6 | TYPE | SNAPSHOTS | +-------------+---------+----------------------+------+------------+-----------+ | container01 | RUNNING | 10.94.217.171 (eth0) | | PERSISTENT | 0 | +-------------+---------+----------------------+------+------------+-----------+ lxc info myhost01:container01 lxc info myhost01:container01 Name: container01 Remote: https://192.168.0.109:8443 Architecture: x86_64 Created: 2016/12/22 03:37 UTC Status: Running Type: persistent Profiles: default Pid: 22659 Ips: eth0: inet 10.94.217.171 vethCIJK85 eth0: inet6 fe80::216:3eff:fe07:69ea vethCIJK85 lo: inet 127.0.0.1 lo: inet6 ::1 Resources: Processes: 81 Disk usage: root: 147.63MB Memory usage: Memory (current): 20.07MB Memory (peak): 42.18MB # .... # While local machine has no containers. lxc list +------+-------+------+------+------+-----------+ | NAME | STATE | IPV4 | IPV6 | TYPE | SNAPSHOTS | +------+-------+------+------+------+-----------+
Also keep this concept in mind even when referencing cached images.
Copying Containers Between Hosts
We will now copy myhost01, container01 (which is running Apache into) into myhost02. The copy is identical except no snapshots and volatile keys are regenerated. For example, the MAC address will be reset and a new host name embedded.
There are two key methods. Clone semi-live using snapshots and shutting down first.
Shutdown Approach
Log into myhost02
lxc stop myhost01:container01 # Verify container stopped lxc list myhost01: +-------------+---------+------+------+------------+-----------+ | NAME | STATE | IPV4 | IPV6 | TYPE | SNAPSHOTS | +-------------+---------+------+------+------------+-----------+ | container01 | STOPPED | | | PERSISTENT | 0 | +-------------+---------+------+------+------------+-----------+ lxc copy myhost01:container01 web01
A copy of container01 has been copied to myhost02 and given the container name web01. Everything is the same except for (...),
lxc list +-------+---------+------+------+------------+-----------+ | NAME | STATE | IPV4 | IPV6 | TYPE | SNAPSHOTS | +-------+---------+------+------+------------+-----------+ | web01 | STOPPED | | | PERSISTENT | 0 | +-------+---------+------+------+------------+-----------+
...
Semi-Live Approach
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Moving Containers
With copy, the new container is identical in every way except no snapshots and volatile keys (ie MAC address and hostnames) will be regenerated.
Creating an exact duplicate or moving a container is a different concept but just as easy.
Current Limitations and Considerations
- Consistency of host IDs which impact containers
- Architecture
- Baselining host patches and OS layer
- ...
Advanced Tuning of Containers
Depending on your needs there are advanced configurations options with LXD. Below are key considerations I think about,
- Security
- Advanced Networking
- Tunnelling ect... as covered in LXC with Advanced Networking
- Joining LXD host networks together
- Capping Resource Utilization
- ...
Reference
Initializing LXD - https://insights.ubuntu.com/2016/03/16/lxd-2-0-installing-and-configuring-lxd-212/
Official Ubuntu Documentation - https://linuxcontainers.org/lxd/getting-started-cli/
Try Online Interactive Tutorial - https://linuxcontainers.org/lxd/try-it/
Remote Container Management - https://www.stgraber.org/2016/03/19/lxd-2-0-your-first-lxd-container-312/
Live Container Migrations - https://bobcares.com/blog/lxc-live-migration-to-minimize-business-downtime/