4.4 Git on the Server - Setting Up the Server

Let’s walk through setting up SSH access on the server side. In this example, you’ll use the authorized_keys method for authenticating your users. We also assume you’re running a standard Linux distribution like Ubuntu.

First, you create a git user account and a .ssh directory for that user.

Next, you need to add some developer SSH public keys to the authorized_keys file for the git user. Let’s assume you have some trusted public keys and have saved them to temporary files. Again, the public keys look something like this:

You just append them to the git user’s authorized_keys file in its .ssh directory:

Now, you can set up an empty repository for them by running git init with the --bare option, which initializes the repository without a working directory:

Then, John, Josie, or Jessica can push the first version of their project into that repository by adding it as a remote and pushing up a branch. Note that someone must shell onto the machine and create a bare repository every time you want to add a project. Let’s use gitserver as the hostname of the server on which you’ve set up your git user and repository. If you’re running it internally, and you set up DNS for gitserver to point to that server, then you can use the commands pretty much as is (assuming that myproject is an existing project with files in it):

At this point, the others can clone it down and push changes back up just as easily:

With this method, you can quickly get a read/write Git server up and running for a handful of developers.

You should note that currently all these users can also log into the server and get a shell as the git user. If you want to restrict that, you will have to change the shell to something else in the /etc/passwd file.

You can easily restrict the git user account to only Git-related activities with a limited shell tool called git-shell that comes with Git. If you set this as the git user account’s login shell, then that account can’t have normal shell access to your server. To use this, specify git-shell instead of bash or csh for that account’s login shell. To do so, you must first add the full pathname of the git-shell command to /etc/shells if it’s not already there:

Now you can edit the shell for a user using chsh <username> -s <shell>:

Now, the git user can still use the SSH connection to push and pull Git repositories but can’t shell onto the machine. If you try, you’ll see a login rejection like this:

At this point, users are still able to use SSH port forwarding to access any host the git server is able to reach. If you want to prevent that, you can edit the authorized_keys file and prepend the following options to each key you’d like to restrict:

The result should look like this:

Now Git network commands will still work just fine but the users won’t be able to get a shell. As the output states, you can also set up a directory in the git user’s home directory that customizes the git-shell command a bit. For instance, you can restrict the Git commands that the server will accept or you can customize the message that users see if they try to SSH in like that. Run git help shell for more information on customizing the shell.