[gentoo-genkernel] [RFC] Genkernel4 and Geninitramfs plan

[Amadeusz Żołnowski]

As of my announcement post 20120901114601.4669.56900@localhost I present
the plan for Genkernel4 and Geninitramfs.  I am waiting for your
comments.


Geninitramfs
~~~~~~~~~~~~

Internal initramfs generator is going to be extracted from Genkernel3
and named Geninitramfs.  It will live with its own life independently
from Genkernel.  It will be quite simple:

1) Copy genkernel repository to new geninitramfs repository.
2) Remove kernel build parts from geninitramfs.
3) Replace "genkernel" name with "geninitramfs" in help, man page,
config, and so on.

Voilà!

Geninitramfs is going to be extracted not earlier than Genkernel4 is
usable with Dracut to avoid synchronization work between Geninitramfs
and Genkernel3.


Genkernel4
~~~~~~~~~~

Genkernel4 is going to be rewritten from scratch in Bash4 and possibly
with some help of Python if necessary.  Genkernel4 is going to:

- build kernel, modules
- build initramfs with Dracut or Geninitramfs (or possibly some other
  tool in the future - initramfs-tools maybe?)
- install kernel, modules, firmware and initramfs
- add/remove boot manager entries


Genkernel4 workflow
~~~~~~~~~~~~~~~~~~~


01. List versions to (re)build
 
    a) local versions
 
    User with "list -l" argument lists versions installed in /usr/src and
    puts star next to the one to which /usr/src/linux symlink links to.
 
    b) remote versions
 
    User with "list -r <version-mask>" argument lists versions at
    kernel.org which could be downloaded and extracted to /usr/src.  Why
    this option while gentoo-sources and others are installed by portage?
    Because some people prefer that portage doesn't register kernel
    sources in vdb.
 
02. Select version
 
    a) local
 
    User selects one of versions listed with "list -l" with arguments
    "select -l <version>/<position of version on the list>".  The check
    if sources still exist is done and the choice is remembered.
 
    b) remote
 
    User selects one of versions listed with "list -r" which doesn't
    exist in /usr/src with arguments "select -r <version>/<position of
    version on the list>".  It is checked if this particular version
    could be downloaded and the choice is remembered.
 
03. Fetch sources if user has chosen "remote"
 
    Tarball is fetched from kernel.org and extracted to /usr/src.
 
04. Setup sources
 
    Symlink to selected (and fetched) sources is set.
 
05. Prepare sources
 
    a) clean
       - make mrproper
 
    b) copy config
 
    Config file is copied from previous version (/proc/config.gz) or from
    location pointed by user.
 
06. Configure sources
 
    - make oldconfig/silentoldconfig/defconfig/...
    - make config/menuconfig/nconfig/... if user wants to
 
07. Build kernel and modules
 
    Runs "make" with CFLAGS, LDFLAGS, and JOBS given by user (in
    config file).
 
08. Install modules and firmware
 
    - make modules_install firmware_install
 
09. Run module-rebuild rebuild if present
 
    It could also be a kind of hook defined in config file, for example:
 
    POST_MODULES_INSTALL_HOOK="module-rebuild rebuild"

10. Build initramfs

    An initramfs is going to be build either by Dracut or by
    Geninitramfs.  I'd like to avoid using command line options of
    Genkernel to pass to Geninitramfs or Dracut therefore Geninitramfs
    or Dracut config is going to be used only.

11. Rebuild kernel if initramfs is chosen to be built into kernel

12. Mount /boot if present in /etc/fstab

13. Install kernel

    - make install

14. Install initramfs

    Copies from image from tmp directory to /boot.

15. Update boot manager entries

    Adds appropriate entry to boot manager.

16. Umount /boot if it has been mounted in step 12.


After successful reboot the cleanup could be made either by user command
or automatically with some startup script.  Following items could be
removed:

1. old trees in /lib/modules
2. old config, System.map and vmlinuz files from /boot
3. old initramfs image from /boot
4. old entries from boot manager
5. clean/mrproper old sources
6. (optionally) old sources if not managed by portage


-- 
Amadeusz Żołnowski