Computer Science Docker

This section is for people who run their own Linux systems. If you're using a system that we run, such as the ilab systems, please see the next section.

If you can do su or sudo, you can do a normal Docker installation. You can install it using apt (Ubuntu) or yum (Centos), or get the most recent release directy from the Docker web page. But there's one thing you must do first .

If you simply install Docker without doing anything else, your system may lose access to the network. To prevent this, before installing Docker create the file /etc/docker/daemon.json . It should contain the following:

{
  "bip": "192.168.100.2/24",
  "mtu": 1500
}

One other warning: Docker images and volumes must be on a local disk. Docker doesn't work with NFS, i.e. file systems mounted from file servers. On most systens, your home directory is on a file server. So make sure you put Docker files on /usr, /var, /freespace, etc.

Until recently, Docker could only be used by people who could do su or sudo. However the most recent release can be used by normal users. Here is a page that describes that: Run the Docker daemon as a non-root user .

However there are some things you must do before you try this out on one of the systems we run. The example below shows all of these things.

• You must make sure you have an entry in /etc/subuid and /etc/subgid The command sudo /usr/libexec/addsubusers.py will do this. If the command doesn't work, please ask help@cs.rutgers.edu to install the necessary files on your system.
• Docker's files won't work over the network. Our user directories are mounted from network file servers. So you have to arrange for Docker to put files on a local file system. On many of our systems, you can create a directory on /freespace/local. The commands below do that. First, do a df and verify that there's at least 10G free on that file system. If not, please send email to help@cs.rutgers.edu.
• Docker uses its own network internally. Unfortunately this network conflicts with networks used by many of our systems. We recommend that you create a file .config/docker/daemon.json that tells Docker to use a different network.
• On you next login, if your non root docker is not running, you can check its status via this command. systemctl --user status docker If it is not running, you can run it again via: systemctl --user start docker If it fails to start, make sure that you are running your docker on the same machine you setup your docker because it sits in a local filesystem.

Installing & Setting up Docker as a User without root

Here's an example of installing Docker as a user. Follow below, if you are setting up docker on the first iLab machine.

df -h /freespace/local
#if /freespace/local has less than 15GB, use another machine
 
# WARNING: we may remove files from /freespace between semesters.
# Because this setup uses /freespace/local, this setup is only
# effective on machine you setup this docker.
# Note: /freespace/local is a local filesystem, therefore
# its content is only available locally.

# make a directory for docker on a local file system
mkdir -p /freespace/local/$USER/docker

# link it to where docker expects it to be
mkdir -p ~/.local/share
ln -s /freespace/local/$USER/docker ~/.local/share
sudo /usr/libexec/addsubusers.py
# if the previous command fails, contact help@cs.rutgers.edu
# the system you're usin isn't properly set up

# create the network config file
mkdir -p ~/.config/docker
cp /etc/docker/daemon.json ~/.config/docker/daemon.json

# now do the installation as documented on the web page
# make sure we start in the home directory
cd
curl -fsSL https://get.docker.com/rootless | sh

### up to here should only be done once
### below here has to be done every time you login

# the curl command will print two export commands. do them
export PATH="$HOME/bin:$PATH"
export DOCKER_HOST=unix://$XDG_RUNTIME_DIR/docker.sock

# put those two export commands in .bashrc if you are
# going to do this a lot

# you must do the following command again every time
# you login.
systemctl --user start docker
# verify that docker started with no errors
systemctl --user status docker

# now try it. fetch a copy of alpine and run it 
# To give docker access to /freespace/local 
# add -v hostpath/dockerpath parameter.
# You can add multiple -v options for more disks.
# I've picked alpine because it's a Linux system, but it's only 5 MB
docker run -v /freespace/local:/freespace/local -it alpine  
# you'll get a prompt like / #
# try something that uses the network
apk update

# exit back to your normal shell
 exit

 

If you are planning to run docker on another iLab machine,

only the following needs to be done on additional machines.

df -h /freespace/local
#if /freespace/local has less than 15GB, use another machine
 
# WARNING: we may remove files from /freespace between semesters.
# Because this setup uses /freespace/local, this setup is only
# effective on machine you setup this docker.
# Note: /freespace/local is a local filesystem, therefore
# its content is only available locally.


  # add entries to /etc/subuid and /etc/subgid
sudo /usr/libexec/addsubusers.py
# if the previous command fails, contact help@cs.rutgers.edu
# the system you're usin isn't properly set up


# make a directory for docker on a local file system
mkdir -p /freespace/local/$USER/docker

# you must do the following command again every time
# you login.
systemctl --user start docker
# verify that docker started with no errors
systemctl --user status docker

# now try it. fetch a copy of alpine and run it 
# To give docker access to /freespace/local 
# add -v hostpath/dockerpath parameter.
# You can add multiple -v options for more disks.
# I've picked alpine because it's a Linux system, but it's only 5 MB
docker run -v /freespace/local:/freespace/local -it alpine  
# you'll get a prompt like / #
# try something that uses the network
apk update

# exit back to your normal shell
 exit