Hello Everyone,
I would like to update everyone on the status of the new image format I
am developing.
It became obvious throughout the course of working with this new
development environment that there would need to be some flexibility in
the image format. I hope I have found a pretty good solution to that
problem...
Old image format:
- writes directly to CF
- uses GRUB
- difficult to upgrade, re-partition, etc
New Image format:
- install AstLinux loader on vfat formatted CF
- boot kexec kernel using syslinux
- boot AstLinux kernel using kexec
- mount root, kd, etc. filesystems using loopback/union
Here is how it would look:
CF:
/bzImage (kexec kernel) - part of AstLinux loader
/syslinux.cfg - AstLinux loader/AstLinux config file
/AstLinux-0.4.0.img - AstLinux root filesystem
/AstLinux-0.4.0.img.sha1 - checksum
/kd.img - AstLinux keydisk (can be stored anywhere)
In this scenario, to upgrade, all you would have to do is download a
new AstLinux image:
CF:
/bzImage (kexec kernel) - part of AstLinux loader
/syslinux.cfg - AstLinux loader/AstLinux config file
/AstLinux-0.4.0.img - AstLinux root filesystem
/AstLinux-0.4.0.img.sha1 - checksum
/AstLinux-0.4.1.img - AstLinux root filesystem
/AstLinux-0.4.1.img.sha1 - checksum
/kd.img - AstLinux keydisk (can be stored anywhere)
The AstLinux loader/kexec kernel (and it's initrd) would automatically
find the newest AstLinux image and verify it's checksum. It would then
mount the image and boot it for you automatically. Of course, your
keydisk would remain compatible.
There are several advantages to using kexec/syslinux:
- Boot AstLinux over the network. While you could always do this with
PXE, this is much more flexible because you can load the AstLinux image
from anywhere (within the capabilities of the AstLinux loader). This
includes FTP, TFTP, HTTP, NFS, etc.
- No fixed image format. The actual CF/HD is always formatted vfat, so
you don't have to worry about partition tables, etc.
- Easy upgrades. This would not be possible without kexec.
- Faster reboots. Most people use kexec just to speed up reboots.
Sounds good to me!
I should have this all working in the next day or so, but I would like
everyone's input for suggestions, etc.
--
Kristian Kielhofner
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