Mailinglist Archive: opensuse-factory (193 mails)
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faster reboot with kexec, debugging panics with kdump
- From: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@xxxxxxx>
- Date: Thu, 12 Jan 2006 00:36:54 +0100
- Message-id: <43C59696.4040402@xxxxxxx>
Hi,
it seems kexec support was merged in the latest SUSE 10.1 snapshot.
This enables you to skip the BIOS when rebooting. Especially if
your BIOS is slow/buggy/whatever, this is a really nice feature
to have.
To test it, install kexec-tools from latest factory snapshot and
a recent kernel (those from factory are recent enough).
Boot into single user.
# kexec -l --command-line="`cat /proc/cmdline`" --initrd=/boot/initrd /boot/vmlinuz
# remount ro /
# kexec -e
You should now see the new kernel booting. I have had success with
both my recent Samsung laptop and an old 600 MHz machine with SCSI.
The time saved (compared to a normal reboot) was:
Samsung laptop, 1600 MHz: 12 seconds
No-name machine, 600 MHz, SCSI disks/cdrom: 31 seconds
If you always hated the time it takes to reboot a server or your
home machine, that might make you happy.
Benefits of kexec:
- Reboot is faster
- The BIOS has no chance to throw errors on you
- The above is especially true if you use FakeRAID controllers
- You don't have to wait until the SCSI controller has enumerated
all devices
- You don't depend on a working GRUB or LILO configuration
- You could even abuse it to install a newer version of SUSE Linux
without booting from CD/DVD/floppy
Caveats:
- Some hardware might not work after kexec'ing the new kernel.
This can be fixed in the driver for that hardware
- Video problems like no display or corrupted display are possible.
Please try "kexec -e --reset-vga" as last command or disable
vesafb
- Somebody needs to hack /sbin/reboot to kexec an already loaded
kernel if there is one
Additional cool features (kdump):
- You might use kexec to load a special crashdump kernel which is
started if your kernel panics. That kernel can save all relevant
debugging info and write it to disk safely, even if the panic
happens while you're using X11 or there is some other reason why
you can't see or capture the panic
- Unfortunately, I can't get kdump to run on my machine, but you
might be luckier
Hey, if we're lucky and it works for everyone, we might even get
kexec supported as optional fastrebooting solution.
Regards,
Carl-Daniel
--
http://www.hailfinger.org/
it seems kexec support was merged in the latest SUSE 10.1 snapshot.
This enables you to skip the BIOS when rebooting. Especially if
your BIOS is slow/buggy/whatever, this is a really nice feature
to have.
To test it, install kexec-tools from latest factory snapshot and
a recent kernel (those from factory are recent enough).
Boot into single user.
# kexec -l --command-line="`cat /proc/cmdline`" --initrd=/boot/initrd /boot/vmlinuz
# remount ro /
# kexec -e
You should now see the new kernel booting. I have had success with
both my recent Samsung laptop and an old 600 MHz machine with SCSI.
The time saved (compared to a normal reboot) was:
Samsung laptop, 1600 MHz: 12 seconds
No-name machine, 600 MHz, SCSI disks/cdrom: 31 seconds
If you always hated the time it takes to reboot a server or your
home machine, that might make you happy.
Benefits of kexec:
- Reboot is faster
- The BIOS has no chance to throw errors on you
- The above is especially true if you use FakeRAID controllers
- You don't have to wait until the SCSI controller has enumerated
all devices
- You don't depend on a working GRUB or LILO configuration
- You could even abuse it to install a newer version of SUSE Linux
without booting from CD/DVD/floppy
Caveats:
- Some hardware might not work after kexec'ing the new kernel.
This can be fixed in the driver for that hardware
- Video problems like no display or corrupted display are possible.
Please try "kexec -e --reset-vga" as last command or disable
vesafb
- Somebody needs to hack /sbin/reboot to kexec an already loaded
kernel if there is one
Additional cool features (kdump):
- You might use kexec to load a special crashdump kernel which is
started if your kernel panics. That kernel can save all relevant
debugging info and write it to disk safely, even if the panic
happens while you're using X11 or there is some other reason why
you can't see or capture the panic
- Unfortunately, I can't get kdump to run on my machine, but you
might be luckier
Hey, if we're lucky and it works for everyone, we might even get
kexec supported as optional fastrebooting solution.
Regards,
Carl-Daniel
--
http://www.hailfinger.org/
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