Gastón Ramos

What is warden?

"The project's primary goal is to provide a simple API for managing isolated environments. These isolated environments -- or containers -- can be limited in terms of CPU usage, memory usage, disk usage, and network access. As of writing, the only supported OS is Linux."

read more here: https://github.com/cloudfoundry/warden/tree/master/warden

Warden is a key component in the Cloud Foundry ecosystem. When you push a new app to Cloud Foundry a new container will be created.

So, lets go to the point, the idea is to install warden in a debian wheezy system, I added debian support to warden in my fork in the Altoro's repo: https://github.com/Altoros/warden

In order make a fresh installation we are going to use vagrant with virtualbox provider, lets start downloading the vagrant box from http://www.vagrantbox.es/.

axel -n 10 http://downloads.shadoware.org/wheezy64.box

Then add the new box to vagrant:

vagrant box add debian-wheezy64 wheezy64.box

Then list all the available boxes to see if it was added ok:

vagrant box list

and you should see something like that:

debian-wheezy64      (virtualbox)
precise64            (virtualbox)

Then lets create a new folder and create our vagrant VM using the box that we just already added:

mkdir testing-warden-on-debian
cd testing-warden-on-debian
vagrant init debian-wheezy64

Now we are ready to start installing warden in the VM:

vagrant ssh
sudo apt-get install -y build-essential debootstrap quota

Edit fstab and add this line:

sudo vi /etc/fstab
cgroup  /sys/fs/cgroup  cgroup  defaults  0   0

Now clone the warden repo and checkout the add-debian-rootfs branch

git@github.com:Altoros/warden.git
cd warden
git checkout add-debian-rootfs

add warden as shared folder in Vagrant file

edit Vagrant file and add this line:

config.vm.synced_folder "warden", "/warden"

then login into the vm with ssh and install all required gems:

vagrant ssh

cd /warden
sudo gem install bundler
sudo bundle

edit config/linux.yml and change the container_rootfs_path, if you don't change it the setup will be lost after you reboot the vm because it is pointed to /tmp by default. I've created a new dir in /tmp-warden and pointed the root_fs to it.

After that you can run the setup

sudo bundle exec rake setup[config/linux.yml]

and when it finishes you will be able to start the warden server:

sudo bundle exec rake warden:start

and then run the client to be able to manage containers:

bundle exec bin/warden

Lets run some basic warden commands:

Create 2 new containers:

bundle exec bin/warden
warden> create
handle : 171hpgcl82u
warden> create
handle : 171hpgcl82v
warden>

List the already created containers:

warden> list
handles[0] : 171hpgcl82u
handles[1] : 171hpgcl82v
warden>

You can see the directories of the containers, replace [tmp-warden] with the folder that your filled in the config/linux.yml:

ls -l /[tmp-warden]/warden/containers/
drwxr-xr-x 9 root root 4096 Jul 15 13:55 171hpgcl82u
drwxr-xr-x 9 root root 4096 Jul 15 13:58 171hpgcl82v
drwxr-xr-x 2 root root 4096 Jul 15 12:18 tmp

If you take a look to the logs while you create a container, you can figure out that this is the flow more or less:

1. method: "set_deferred_success"

/home/gramos/src/altoros/warden/warden/lib/warden/container/spawn.rb

2. Create the container

/home/gramos/src/altoros/warden/warden/root/linux/create.sh /[tmp-warden]/warden/containers/171hpgcl831

3. method:"do_create"

   /home/gramos/src/altoros/warden/warden/lib/warden/container/linux.rb

4. Start the container

  /[tmp-warden]/containers/171hpgcl831/start.sh

5. method: "write_snapshot"

  /home/gramos/src/altoros/warden/warden/lib/warden/container/base.rb

6. method: "dispatch"

  /home/gramos/src/altoros/warden/warden/lib/warden/container/base.rb

And thats all, if you have any comments feel free to post them here!