Running Alpine Linux containers on LXD

2016-01-19 by saghul Leave a comment

So, more LXD! Today we are going to run some Alpine Linux containers on LXD. Why? Alpine describe themselves as a “security-oriented, lightweight Linux distribution based on musl libc and busybox.”, what’s there not to like? It has become quite popular in the Docker world due to the small yet fully functional containers one can create.

Building an Alpine container on LXD is not that straightforward, however. There are no Alpine images on the official repo, so we will have to build our own. LXD does provide some documentation on how an image should be like, lo let’s get to it!

I started by taking a look at the template for LXC. That was close enough, so I went ahead and modified it in order to create LXD images. That resulted in lxd-alpine-builder.

With that script, we can now create an image and then import it into LXD:

sudo ./build-alpine
lxc image import alpine-v3.3-x86_64-20160114_2308.tar.gz --alias alpine-v3.3

That image is 2.39MB, w00t! You can check it by listing the images:

saghul@lxd-test:~$ lxc image list
+----------------------------+--------------+--------+---------------------------------+--------+----------+-------------------------------+                                                                      
|           ALIAS            | FINGERPRINT  | PUBLIC |           DESCRIPTION           |  ARCH  |   SIZE   |          UPLOAD DATE          |                                                                      
+----------------------------+--------------+--------+---------------------------------+--------+----------+-------------------------------+                                                                      
| alpine-v3.3                | 9888dd281789 | no     | alpine v3.3 (20160114_23:08)    | x86_64 | 2.39MB   | Jan 14, 2016 at 11:10pm (CET) |                                                                      
| jessie-amd64               | 9f065ac6be10 | no     | Debian jessie (amd64)           | x86_64 | 102.66MB | Jan 12, 2016 at 4:17pm (CET)  |                                                                      
| jessie-amd64-base          | b85a1bdb5057 | no     | Debian Jessie base              | x86_64 | 87.98MB  | Jan 12, 2016 at 9:56am (CET)  |                                                                      
| jessie-amd64-base-sysvinit | 628b7f8470af | no     | Debian Jessie base (no systemd) | x86_64 | 82.91MB  | Jan 12, 2016 at 11:40am (CET) |                                                                      
| jessie-i386                | 769f90666ea8 | no     | Debian jessie (i386)            | i686   | 100.23MB | Jan 15, 2016 at 9:54am (CET)  |                                                                      
+----------------------------+--------------+--------+---------------------------------+--------+----------+-------------------------------+

Now we can launch a container and test it out!

lxc launch alpine-v3.3 alpinetest
lxc exec alpinetest /bin/ash
# cat /etc/alpine-release 
3.3.1

Happy containering!

Simple networking for your LXD containers

2016-01-18 by saghul Leave a comment

So, more LXD, here we go! Today we are going to see how to access our LXD containers from outside of the system running LXD itself.

If you are just trying out stuff (like I am), you probably installed some Ubuntu version on a VM in order to run LXD. This means that by default you have no access to your containers from your system, just from the system running LXD.

A simple solution is to add a route to the isolated network that the container get, going through the host running LXD:

ip route add addr:10.0.3.0/24 via 192.168.99.28

Here we are telling our system that the 10.0.3.0/24 network is routable through 192.168.99.28, our LXD machine.

You probably don’t want to use something like this in production, but we are exporing here! 🙂

LXD, Debian containers and systemd

2016-01-15 by saghul Leave a comment

I have been playing around with LXD the past few nights, and so far I really like it. It’s like VMs, but as a container, in contrast with Docker, which is designed around running a single application as a container.

In order to try LXD out I installed a Ubuntu 15.10 VM and added the LXD stable PPA. Then it was time to launch some containers!

lxc remote add images images.linuxcontainers.org
lxc image copy images:debian/jessie/amd64 local: --alias jessie-amd64
lxc launch jessie-amd64 jessie-test

Shortly after I hit a problem: I could not stop the container I just created! It would just hang there, so I had to stop it forcefully:

lxc stop --force jessie-test

That doesn’t look good at all. Digging around I found the issue on GitHub, which basically concludes that it’s a systemd issue, because it doesn’t seem to handle SIGPWR correctly. Oh boy. The systemd issue is still open on Launchpad, so what do we do then? Well, we get rid of systemd. Let’s prepare a base Debian Jessie image with good old SysV init, shall we?

lxc exec jessie-test /bin/bash
apt-get update && apt-get install sysvinit-core
exit
lxc stop jessie-test --force
lxc start jessie-test
lxc exec jessie-test /bin/bash
apt-get remove --purge --auto-remove systemd
rm -rf /var/lib/apt/lists/*
rm -rf /var/cache/apt/archives/*
exit
lxc stop jessie-test
lxc publish jessie-test --alias jessie-amd64-base-sysvinit

Now all containers we create with our new and shiny image will stop gracefully.