Creating a pre-receive hook environment

A pre-receive environment for GitHub Enterprise Server is a Linux chroot environment. Because pre-receive hooks execute on every push event, they should be fast and lightweight. The environment needed for such checks will typically be minimal.

GitHub Enterprise Server provides a default environment which includes these packages: awk, bash, coreutils, curl, find, gnupg, grep, jq, sed.

If you have a specific requirement that isn't met by this environment, such as support for a particular language, you can create and upload your own 64-bit Linux chroot environment.

The Git version used in the pre-receive hook environment must be at least 2.11, or if you are using libgit2 you must use at least version 0.18. If you are using another Git implementation, it must support relative paths in the info/alternates file.

Creating a pre-receive hook environment using Docker

You can use a Linux container management tool to build a pre-receive hook environment. This example uses Alpine Linux and Docker.

1. Ensure Docker is installed locally.

2. Create the file Dockerfile.alpine that contains this information:

   FROM alpine:latest
   RUN apk add --no-cache git bash
   

3. From the working directory that contains Dockerfile.alpine, build an image:

   $ docker build -f Dockerfile.alpine -t pre-receive.alpine .
   > Sending build context to Docker daemon 12.29 kB
   > Step 1 : FROM alpine:latest
   >  ---> 8944964f99f4
   > Step 2 : RUN apk add --no-cache git bash
   >  ---> Using cache
   >  ---> 0250ab3be9c5
   > Successfully built 0250ab3be9c5
   

4. Create a container:

   docker create --name pre-receive.alpine pre-receive.alpine /bin/true
   

5. Export the Docker container to a gzip compressed tar file:

   docker export pre-receive.alpine | gzip > alpine.tar.gz
   

   This file alpine.tar.gz is ready to be uploaded to the GitHub Enterprise Server appliance.

Creating a pre-receive hook environment using chroot

1. Create a Linux chroot environment.

2. Create a gzip compressed tar file of the chroot directory.

   cd /path/to/chroot
   tar -czf /path/to/pre-receive-environment.tar.gz .
   

   Note

   • Do not include leading directory paths of files within the tar archive, such as /path/to/chroot.
   • /bin/sh must exist and be executable, as the entry point into the chroot environment.
   • Unlike traditional chroots, the dev directory is not required by the chroot environment for pre-receive hooks.

For more information about creating a chroot environment see "Chroot" from the Debian Wiki, "BasicChroot" from the Ubuntu Community Help Wiki, or "Installing Alpine Linux in a chroot" from the Alpine Linux Wiki.

Uploading a pre-receive hook environment on GitHub Enterprise Server

1. In the top-right corner of GitHub Enterprise Server, click your profile photo, then click Enterprise settings.

   

2. On the left side of the page, in the enterprise account sidebar, click Settings.

3. Under " Settings", click Hooks.

4. Click Manage environments.

5. Click Add environment.

6. In the "Environment name" field, enter the desired name.

7. In the "Upload environment from a URL" field, enter the URL of the *.tar.gz file that contains your environment.

8. Click Add environment.

Uploading a pre-receive hook environment via the administrative shell

1. Upload a readable *.tar.gz file that contains your environment to a web host and copy the URL or transfer the file to the GitHub Enterprise Server appliance via scp. When using scp, you may need to adjust the *.tar.gz file permissions so that the file is world readable.

2. Connect to the administrative shell.

3. Use the ghe-hook-env-create command and type the name you want for the environment as the first argument and the full local path or URL of a *.tar.gz file that contains your environment as the second argument.

   admin@ghe-host:~$ ghe-hook-env-create AlpineTestEnv /home/admin/alpine.tar.gz
   > Pre-receive hook environment 'AlpineTestEnv' (2) has been created.