Running a Git Server

#### Beyond Linux® From Scratch (systemd Edition) - Version 12.2

### Chapter 13. Programming

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# Running a Git Server

## Introduction

This section will describe how to set up, administer and secure a git server. Git has many options available. For more detailed documentation see https://git-scm.com/book/en/v2.

### Server Dependencies

#### Required

git-2.46.0 and OpenSSH-9.8p1

## Setting up a Git Server

The following instructions will install a git server. It will be set up to use OpenSSH as the secure remote access method.

Configuration of the server consists of the following steps:

### 1. Set Up Users, Groups, and Permissions

You will need to be user `root` for the initial portion of configuration. Create the `git` user and group and set and unusable password hash with the following commands:

    groupadd -g 58 git &&
    useradd -c "git Owner" -d /home/git -m -g git -s /usr/bin/git-shell -u 58 git &&
    sed -i '/^git:/s/^git:[^:]:/git:NP:/' /etc/shadow

Putting in an unusable password hash (replacing the `!` by `NP`) unlocks the account but it cannot be used to login via password authentication. That is required by sshd to work properly. Next, create some files and directories in the home directory of the git user allowing access to the git repository using ssh keys.

    install -o git -g git -dm0700 /home/git/.ssh &&
    install -o git -g git -m0600 /dev/null /home/git/.ssh/authorized_keys

For any developer who should have access to the repository add his/her public ssh key to `/home/git/.ssh/authorized_keys`. First, prepend some options to prevent users from using the connection to git for port forwarding to other machines the git server might reach.

    echo -n "no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty " >> /home/git/.ssh/authorized_keys &&
    cat <user-ssh-key> >> /home/git/.ssh/authorized_keys

It is also useful to set the default name of the initial branch of new repositories by modifying the git configuration. As the `root` user, run:

    git config --system init.defaultBranch trunk

Finally add the `/usr/bin/git-shell` entry to the `/etc/shells` configuration file. This shell has been set in the `git` user profile and is to make sure that only git related actions can be executed:

    echo "/usr/bin/git-shell" >> /etc/shells

### 2. Create a git repository

The repository can be anywhere on the filesystem. It is important that the git user has read/write access to that location. We use `/srv/git` as base directory. Create a new git repository with the following commands (as the `root` user):

### Note

In all the instructions below, we use project1 as an example repository name. You should name your repository as a short descriptive name for your specific project.

    install -o git -g git -m755 -d /srv/git/project1.git &&
    cd /srv/git/project1.git                             &&
    git init --bare                                      &&
    chown -R git:git .

### 3. Populate the repository from a client system

### Note

All the instructions in this section and the next should be done on a user system, not the server system.

Now that the repository is created, it can be used by the developers to put some files into it. Once the ssh key of the user is imported to git's `authorized_keys` file, the user can interact with the repository.

A minimal configuration should be available on the developer's system specifying its user name and the email address. Create this minimal config file on client side:

    cat > ~/.gitconfig <<EOF
    [user]
            name = <users-name>
            email = <users-email-address>
    EOF

On the developer's machine, set up some files to be pushed to the repository as the initial content:

### Note

The gitserver term used below should be the host name (or ip address) of the git server.

    mkdir myproject
    cd myproject
    git init --initial-branch=trunk
    git remote add origin git@gitserver:/srv/git/project1.git
    cat >README <<EOF
    This is the README file
    EOF
    git add README
    git commit -m 'Initial creation of README'
    git push --set-upstream origin trunk

The initial content is now pushed to the server and is available for other users. On the current machine, the argument `--set-upstream origin trunk` is now no longer required as the local repository is now connected to the remote repository. Subsequent pushes can be performed as

    git push

Other developers can now clone the repository and do modifications to the content (as long as their ssh keys has been installed):

    git clone git@gitserver:/srv/git/project1.git
    cd project1
    vi README
    git commit -am 'Fix for README file'
    git push

### Note

This is a very basic server setup based on OpenSSH access. All developers are using the `git` user to perform actions on the repository and the changes users are committing can be distinguished as the local user name (see `~/.gitconfig`) is recorded in the changesets.

Access is restricted by the public keys added to git's `authorized_keys` file and there is no option for the public to export/clone the repository. To enable this, continue with step 4 to set up the git server for public read-only access.

In the URL used to clone the project, the absolute path (here `/srv/git/project1.git`) has to be specified as the repository is not in git's home directory but in `/srv/git`. To get rid of the need to expose the structure of the server installation, a symlink can be added in git's home directory for each project like this:

    ln -svf /srv/git/project1.git /home/git/

Now, the repository can be cloned using

    git clone git@gitserver:project1.git

### 4. Configure the Server

The setup described above makes a repository available for authenticated users (via providing the ssh public key file). There is also a simple way to publish the repository to unauthenticated users — of course without write access.

The combination of access via ssh (for authenticated users) and the export of repositories to unauthenticated users via the daemon is in most cases enough for a development site.

### Note

The daemon will be reachable at port `9418` by default. Make sure that your firewall setup allows access to that port.

To start the server at boot time, install the `git-daemon.service` unit from the blfs-systemd-units-20240801 package:

    make install-git-daemon

In order to allow git to export a repository, a file named `git-daemon-export-ok` is required in each repository directory on the server. The file needs no content, just its existence enables, its absence disables the export of that repository.

    touch /srv/git/project1.git/git-daemon-export-ok

Along with the `git-daemon.service` unit, a configuration file named `/etc/default/git-daemon` has been installed. Review this configuration file to match your needs.

There are only three options to set in the configuration file:

- GIT_BASE_DIR=<dirname>

  Specify the location of the git repositories. Relative paths used when accessing the daemon will translated relative to this directory.

- DFT_REPO_DIR=<dirname>

  This directory is added to the white list of allowed directories. This variable can hold multiple directory names but is usually set equal to `GIT_BASE_DIR`.

- GIT_DAEMON_OPTS=<options>

  In case special options to the git daemon command are needed, they have to be specified in this setting. One example might be to adjust the port number where daemon is listening. In this case, add `--port=<port number>` to this variable. For more information about which options can be set, take a look at the output of git daemon --help.

After starting the daemon, unauthenticated users can clone exported repositories by using

    git clone git://gitserver/project1.git

As the base directory is `/srv/git` by default (or set to a custom value in the configuration), git interprets the incoming path (/project1.git) relative to that base directory so that the repository in `/srv/git/project1.git` is served.

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