Hello,

recently I fixed a small bug in cockpit [1]. The fix is rather trivial but it was quite difficult to test it and verify that it really fixes the problem.

ALP Prerequisites =================

1. Install ALP from https://download.opensuse.org/repositories/SUSE:/ALP/images/, see the previous mails about the installation and configuration

2. Install cockpit with "transactional-update pkg install cockpit", then reboot the system (the backend packages are already preinstalled in the ALP image, this will install the web frontend)

3. Start the cockpit service: "systemctl enable --now cockpit.socket"

Now you will have the standard cockpit installed and ready to run, you might test it by connecting to https://localhost:9090

Development ===========

Note: I needed to patch a cockpit plugin which is basically a JS code + HTML + CSS. If you would need to patch the cockpit core (the C code) it would be more difficult, see the suggestion in the end.

I did the development directly on my workstation (Leap 15.4), the ALP instance was running in a VM.

Development Prerequisites -------------------------

For patching a cockpit plugin you should not need much libraries installed, but the the Makefile (generated by autotools) requires the libraries also for the C part.

On my workstation I had to additionally install these packages:

zypper install json-glib-devel krb5-devel sassc nodejs16

You might actually need some more libraries or tools (autotools), I use my workstation as a development machine and it already contains a lot of libraries.

Check that nodejs and npm default versions are 16, esp. if you have multiple versions installed. Originally I probably did something wrong and got some strange failures...

Then you can checkout the sources from GitHub

git clone git@github.com:cockpit-project/cockpit.git

and checkout the version used in ALP

cd cockpit git checkout -b 276

Check https://build.opensuse.org/package/show/SUSE:ALP/cockpit, it might change in the future.

To build the sources use:

# this installs the npm packages using "npm install" ./autogen.sh # autogen.sh runs configure but it will very likely fail, by default it needs # some additional libraries, if you want to patch just a plugin then run ./configure --disable-doc --disable-ssh --disable-pcp --disable-polkit make

Now the compiled plugins are available in ./dist/ subdirectory. Now we need to transfer these changed file to the ALP system.

There are several possibilities to do this. You can run an "scp" command after each edit/build or you can use some network file system.

I tested that with sshfs. The disadvantage is that the sshfs packages are not available for ALP, as a workaround I installed the "sshfs" and "fuse3" packages from Tumbleweed. That works currently because ALP is based on TW, but that will probably not work later when ALP is branched from TW. The clean solution would be to provide a container for that...

To mount a directory over sshfs run

sshfs <user>@<machine>:<path_to_git_checkout> /mnt

Now we need cockpit to load the new files. Fortunately it can load the plugins from the user's $HOME:

mkdir ~/.local/share/cockpit

link the shared directory from the development machine

ln -s /mnt/dist/networkmanager/ ~/.local/share/cockpit/networkmanager

(You could link the whole /dist/ to override all plugins, but that could possibly have some side effects, I'd rather just override the updated plugin to be safe.)

Then you can just reload the cockpit page in the web browser and that's it, you do not need to relogin or restart the cockpit service.

Testing with the "main" branch ==============================

Then I wanted to test my change also with the "main" branch to be sure it can be properly submitted to upstream.

It turned out that they changed the way how the node modules are loaded. They do not run "npm install" anymore, but rather use Git submodules for that, the whole "node_modules" directory is a Git submodule.

The problem is that the submodules are not checked out by default. If you want to use the "main" branch then do the initial checkout with

git clone --recurse-submodules git@github.com:cockpit-project/cockpit.git

or if you already have a clone without submodules then you can download them with

git submodule update --init

Be careful when switching the branches! When you later switch to an older version you might need to delete the "node_modules" directory and run ./autogen.sh to install them via npm otherwise you will end up with different modules and probably get some nasty errors!

Patching the Core Cockpit =========================

If you need to patch the C part then you could just run "make" and copy the built binary to the ALP VM.

The problem is that /usr is read-only in ALP. But you can create a writable overlay using overlayfs:

mkdir /tmp/upperdir mkdir /tmp/workdir mount -t overlay overlay -o lowerdir=/usr,upperdir=/tmp/upperdir/,workdir=/tmp/workdir/ /usr

Then the /usr will become writable, see more details in https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt

Now you can easily rewrite or edit the files there

cp /mnt/cockpit-tls /usr/libexec/cockpit-tls

To take effect you need to restart the cockpit service

systemctl restart cockpit

HTH

Ladislav

[1] https://github.com/cockpit-project/cockpit/pull/17776