Getting Your Customized openSUSE Kernel on OBS

Presented at openSUSE.Asia Summit 2024

Transcript

1. How to Maintaining a Linux Kernel Package on openSUSE's Open Build Service Getting Your Customized openSUSE Kernel on OBS Shung-Hsi Yu, SUSE @shunghsiyu @shunghsiyu@fosstodon.org
2. About me Shung-Hsi Yu SUSE Based in Taitung, Taiwan Kernel Engineer BPF Subsystem openSUSE SUSE Enterprise Linux
3. Agenda - Backgrounds - Problems & Rational - How to Customize (the Kernel) - Comparisons (of methods) - Takeaways
4. Backgrounds
5. Linux Kernel - Core of the system - Talks to hardware (w/ drivers) - Provide abstractions/features
6. Open Build Service (OBS) - Build Service - Produce RPM packages - Compile source code to binaries - Hosts RPM packages
7. Open Build Service (OBS) Interface - API - osc command-line tool - WebUI
9. Problems
10. Additional Feature You want additional security hardening with ABC feature, however due to performance impact it is disabled in openSUSE’s kernel # CONFIG_ABC is not set
11. Unsupported Hardware You have XZY device, but openSUSE’s kernel cannot use it because support is not enabled # CONFIG_XZY is not set
12. Unsupported Hardware You have XZY device, but openSUSE’s kernel cannot use it because the driver’s source code is not upstream
13. Distributing and Installation You have built a kernel on your laptop, now you need to have it installed on all your machines
14. Updating the Kernel There a critical security bug the was fixed, do you have to go through the same again?
15. Rational
16. Why Customize? - Missing features / hardware support - Disabled - Not available - Too many features / hardware support - Security - Size
17. Why NOT Customize? - Support on your own - Untested
18. Why use OBS? - Builds RPM packages for you - Make package distribution easy (and secure) - Works well with openSUSE distros - Support many architectures
19. How to Customize Overview
20. #1 - {patches,config}.addon - the “default” way to do customization - patch and config managed in OBS - OBS keeps it updated (w/ link)
21. #2 - kernel-$FLAVOR.spec - lightweight customization - single RPM specification file - repackaging of existing RPM
22. #3 - fork kernel-source.git - openSUSE/SUSE kernel team’s workflow - patches and config managed with git repository
23. How to Customize #1 - {patches,config}.addon
24. Setup Requirements - osc (cmdline) / web browser - tar & gzip bzip2 (cmdline) / GUI archiver - (optional) diff
25. Workflow (changing config) 1. Branch kernel-default project on OBS 2. Create config.addon.tar.bz2 3. Upload to your branched kernel-default OBS project
26. Config Modification $ tree config.addon/ config.addon/ ├── arm64 │ └── default └── x86_64 └── default
27. Config Modification $ cat config.addon/x86_64/default CONFIG_XYZ=y ...
28. Workflow (generating patches) 1. Download source code of kernel.git 2. Extract 3. Modify 4. diff
29. Workflow (adding patches) 1. Branch kernel-default project on OBS 2. Create patches.addon.tar.bz2 3. Upload to your branched kernel-default OBS project
30. Code Modification $ tree . 0001-support-XZY.patch series
31. Code Modification $ cat 0001-support-XZY.patch --- a/drivers/XYZ/main.c +++ b/drivers/XYZ/main.c @@ -93,7 +93,7 @@ ... $ cat series 0001-support-XZY.patch
32. How to Customize #2 - kernel-$FLAVOR.spec
33. Setup Requirements - osc (cmdline) / web browser
34. Workflow (changing spec) 1. Branch kernel-default-base project on OBS 2. Modify kernel-default-base.spec 3. (optional) Rename spec file and project
35. Module Modification $ cat kernel-default-base.spec ... define filesystems autofs4 btrfs ext4 fuse vfat \ isofs jbd2 mbcache nfsv2 ... %define modules %usb_modules %net_drivers \ %scsi_modules %block_drivers hyperv_modules %virtio_modules %vmware_modules %xen_modules ...
36. How to Customize #3 - fork kernel-source.git
37. Setup Requirements - osc - git - quilt - diff - …
38. Workflow (adding patches) 1. Clone kernel-source.git 2. cd kernel-source 3. sequence-patch.sh 4. cd tmp/current 5. add new patch with quilt
39. Workflow (adding patches) 6. quilt edit 7. refresh_patch.sh 8. cd patches (kernel-source) 9. log 10. (optional) git push …
40. Workflow (upload) Push changes to OBS $OBS_BRANCH=home:$USER:branches:Leap:15.6:Update $FLAVOR=default scripts/tar-up.sh scripts/osc_wrapper upload --enable-debug "$OBS_BRANCH" ./kernel-source/kernel-default.spec
41. Comparisons
42. #1 - {config,patches}.addon The Good - good balance between easiness and flexibility The Bad - some chance of patch failing to apply
43. #2 - kernel-$FLAVOR.spec The Good - easy, super fast to build package - identical binaries - low maintenance The Bad - not flexible, can’t add feature / hardware support
44. #3 - fork kernel-source.git The Good - very flexible - remove existing patch and or add new upstream patch - scales very well - many collaborators & many custom patches / changes
45. #3 - fork kernel-source.git The Bad - needs to be updated manually - needs more resources / tooling - workflow is much more complex - uses command-line-only tools
46. Takeaways
47. Takeaways Sometimes you need to customize the Linux Kernel for feature Using openSUSE’s OBS to do so save you resources and makes distributing easy
48. Takeaways (cont.) Start with *.addon customization move to other method if it doesn’t work well
49. Appendix
50. Examples home:tiwai:kernel:sle15-sp6-kasan - customize kernel config with config.addon openSUSE:Leap:15.6:Update/kernel-default-base - customize kernel-default RPM with spec file home:tiwai:kernel:drm-tip - customize kernel config with kernel-source
51. References - How to maintain kernel-source packages on OBS? - How to Modify a Package in Open Build Service - openSUSE:Build Service Collaboration - openSUSE:Build Service Concept project linking - Open Build Service Beginnerʼs Guide - SUSE Kernel Site - kernel-source’s README.SUSE