3

I'm using LXC as a lab platform for testing SaltStack scripts. The lab consists of +5 Ubuntu 12.04 LTS containers, which I create by cloning a template container with salt-minion pre-installed.

Once I create the template container and install salt-minion, the template gets its Salt minion_id based on hostname (test-template). If I lxc-clone this template, all clones will have that template's minion_id, but I would like clones to have minion_id matching their hostname (test-machine-{1,2,3,4,5}).

Is there a way to make this scripted with bash or should I take another path to the same effect?

UPDATE:

I looked into some of lxc scripts and found out that lxc scripts use /usr/share/lxc/lxc.functions file which defines get_default_lxcpath function, so my current script looks something like this:

. /usr/share/lxc/lxc.functions

# clone template
lxc-clone -o $template -n "$container"

# create saltstack minion config dir if does not exist    
minion_id_path="$(get_default_lxcpath)/$container/rootfs/etc/salt"
mkdir -p "$minion_id_path"

# set minion-id directly from container name
echo "$container" > "$minion_id_path/minion_id"                

I don't like this solution since it depends heavily on internals of both lxc and saltstack, but does the job.

UPDATE 2:

After suggestion in comments about how salt-minion will generate new minion_id when existing one is deleted, I reduced this to two commands:

. /usr/share/lxc/lxc.functions

# clone template
lxc-clone -o $template -n "$container"

# delete minion_id to allow salt-minion to generate a new one
rm "$(get_default_lxcpath)/$container/rootfs/etc/salt/minion_id"

I'd still like to see more generic/robust approach not depending on SaltStack and LXC internals.

2
  • 1
    If you delete the minion_id from the template then it should be automatically re-created on the next start up of the salt-name and will take the clone vm's hostname by default. I am not familiar with lxc but does the hostname get set before or after the salt-minion startup? – Jason Zhu Apr 8 '14 at 17:34
  • /etc/hostname is created in the same run when lxc is created. But, that's great hint, because I can replace last two commands with rm. – LavaScornedOven Apr 8 '14 at 17:53
3

Use docker with a dockerfile. You can easily find examples online for both salt-minion and salt-master.

Grab the files and proceed to build the images (it's always a good idea to tag them). Given a directory structure like this one (closely following the examples pointed above):

docker/
├── salt-master
│   ├── Dockerfile
│   └── supervisor-salt.conf
└── salt-minion
    ├── Dockerfile
    └── supervisor-salt.conf

you need to cd docker/salt-master and issue:

# docker build -t kstaken/ubuntu-salt-master .

the equivalent for the salt-minion:

# cd docker/salt-minion
# docker build -t kstaken/ubuntu-salt-minion .

This process creates reusable images:

# docker images | grep kstaken
kstaken/ubuntu-salt-minion   latest              557c052f5b14        19 seconds ago      253.5 MB
kstaken/ubuntu-salt-master   latest              1f41866d05e1        5 minutes ago       262.7 MB

that you can start in the foreground (and attach to them) or in the background, as needed. You can also link them:

# docker run --detach=true --hostname=salt-master --networking=true kstaken/ubuntu-salt-maste
# docker run --detach=true --hostname=minion1 --networking=true --link bersek_morse:linked-server kstaken/ubuntu-salt-minion
# docker run --detach=true --hostname=minion2 --networking=true --link berserk_morse:linked-server kstaken/ubuntu-salt-minion

The result is very easily scriptable:

# docker ps
CONTAINER ID        IMAGE                               COMMAND                CREATED             STATUS              PORTS                NAMES
4fae47241a73        kstaken/ubuntu-salt-minion:latest   /usr/bin/supervisord   4 seconds ago       Up 2 seconds                             goofy_fermi
6030e7f882ba        kstaken/ubuntu-salt-minion:latest   /usr/bin/supervisord   25 seconds ago      Up 23 seconds                            desperate_hawking
22b18a387e21        kstaken/ubuntu-salt-master:latest   /usr/bin/supervisord   3 minutes ago       Up 3 minutes        4505/tcp, 4506/tcp   berserk_morse,desperate_hawking/linked-server,goofy_fermi/linked-server

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.