The yupdate Script

This is a documentation for the yupdate helper script, which is included in the YaST installer in SLE15-SP2/openSUSE Leap 15.2 (or newer) and in the openSUSE Tumbleweed since build 2020xxxx.

The Introduction

Problem: You are developing a feature for the installer and you need to test your changes frequently. For extra fun, the change is spread across multiple repositories.

The YaST installation system is quite different to an usual Linux installed system. The root filesystem is stored in a RAM disk and most files are read-only. That makes it quite difficult to modify the YaST installer if you need to debug a problem or test a fix.

There are some possibilities for updating the YaST installer (see Alternative) but they are usually not trivial and need special preparations. For this reason we created a special yupdate script which makes the process easier.

However, in some cases this easier way cannot be used, see the limitations section below.

Self-update

After patching the installer the yupdate script disables the YaST self-update feature because it could conflict with it and overwrite the changes.

If you need some changes from the self-update then use the startshell=1 boot option, start the installer and allow the self-update step to finish, then abort the installation and use the ypdate script to apply the changes on top of the self-update.

Warning

:warning: Patching the installer with the yupdate script makes the installation unsupported! :warning:

The script is intended for developers to test new features or bug fixes.

It can be used by customers for testing as well, but it should not be used on production systems!

Installation

The yupdate script should run in the inst-sys. Since SLE15-SP2/openSUSE Leap 15.2, openSUSE Tumbleweed 20200314, it is preinstalled.

For older releases, run:

curl https://raw.githubusercontent.com/yast/yast-installation/master/bin/yupdate > /usr/bin/yupdate
chmod +x /usr/bin/yupdate

You can also use this command to update the included script to the latest version.

Basic Use Cases

This script is intended to help in the following scenarios.

Make the inst-sys Writable

As already mentioned, the files in the installation system are read only. To be able to patch the installer the script must be able to make the files writable. It does that automatically for the updated files, but maybe you would like to use this feature also for some other non-YaST files.

To make a directory writable in the inst-sys run command

yupdate overlay create <dir>

This will create a writable overlay above the specified directory. If you do not specify any directory it will create writable overlays for the default YaST directories.

Then you can easily edit the files using the included vim editor or by other tools like sed or overwrite by external files.

Patch YaST from GitHub Sources

To update or install an YaST package directly from the GitHub source code repository use command

yupdate patch <github_slug> <branch>

where github_slug is a user/repository name, if the user value is missing the default "yast" is used. The branch in the source branch to install, for example master or SLE-15-SP2.

Examples

# install the latest version of yast2-installation from upstream
yupdate patch yast-installation master
# install from a fork
yupdate patch my_fork/yast-installation my_branch

Notes

  • Make sure that you use a branch compatible with the running inst-sys, installing the latest version in an older release might not work as expect, the installer might crash or behave unexpectedly.
  • There is no dependency resolution, if the new installed package requires newer dependant packages then they must be installed manually.

Patch YaST from Locally Modified Sources

Installing from GitHub sources is easy, but sometimes you do not want to push every single change to GitHub, you would like to just use the current files from you local Git checkout.

In that case run

rake server

in your YaST module Git checkout. This will run a web server providing source tarball similar to the GitHub archive used in the previous case.

Note: You need "yast-rake" Ruby gem version 0.2.37 or newer.

Then run

yupdate patch <host_name>

where <host_name> is the machine host name or the IP address where you run the rake server task. To make it easier the rake task prints these values at the start.

By default this will use port 8000, if the server uses another port just add : followed by the port number.

Note: Make sure the server port is open in the firewall configuration, see the documentation for more details.

Patching Multiple Packages

The yupdate patch command installs the sources from all running rake server servers. If you need to update sources from several packages you can just run rake server in all of them and install them with a single yupdate call.

Patch YaST from a Generic Tarball Archive

This is similar to the previous cases, but the source tarball is not generated dynamically by a server, but it is a statically hosted file.

Example:

yupdate patch http://myserver.example.com/test/yast2.tar.gz

Other Commands

Listing OverlayFS Mounts

To see the list of mounted OverlayFS run

yupdate overlay list

Listing Updated Files

To see the list of changed files

yupdate overlay files

Displaying Changes in the System

To see the applied changes to the system run

yupdate overlay diff

This will display a diff for all changed files, it does not report deleted or new files.

Restoring the System

To revert all changes run

yupdate overlay reset

This will remove all OverlayFS mounts and restore the system to the original state.

Limitations

  • The script only works with Ruby source files, it cannot compile and install C/C++ or other sources (the compiler and development libraries are missing in the inst-sys)
  • Works only with the packages which use Rakefile for installation, it does not work with autotools based packages (again, autoconf/automake are also missing in the inst-sys)
  • It patches only the files in the inst-sys, the target installed system will contain the original files from the installation medium. That also means the AutoYaST second stage cannot be fixed by yupdate, you need to build a DUD, see below.

Alternative

  1. For all repos, run rake osc:build
  2. Collect the resulting RPMs
  3. Run a server, eg. with ruby -run -e httpd -- -p 8888 .
  4. Type a loooong boot line to pass them all as DUD=http://....rpm (or write that into a file and use the info option or build a single DUD file from the RPMs with the mkdud script)

Implementation Details

OverlayFS

To make the inst-sys directories writable we use the Linux OverlayFS which can merge already existing file systems ("union filesystem").

See more details in the Linux Kernel Documentation.

Installing the Files

For installing the sources the script uses the rake install DESTDIR=... command and install the files into a temporary directory. Then it compares the new files with the original files and if there is a change the old file is rewritten by the new file.

This also skips some not needed files like documentation, manual pages, editor backup files, etc...

This saves some memory as we do not need to shadow the not modified files with the same content.

Logging

The messages printed on the console are also saved in the y2log file. That means it should be easy to find out that someone patched the installer when analyzing logs from a bug report.