booting read only

drkstr · 07-15-2006, 12:47 AM

I'm trying to boot my system in ro, but for the system to boot correctly /var and /dev need to be loaded into a ramdisk. I was able to get /var loaded into the ramdisk by copying the directory to /lib/var then adding the following lines to the beginning of my rc.S

Code:

echo "Loading /var to ramdisk"
mke2fs -q -I 1024 /dev/ram1 4096
mount /dev/ram1 /var -o defaults,rw
cp -a /lib/var /

The system will boot (if you don't mind all the errors about not being able to write to /dev) and when I log in, /var is sucsessfully loaded into the ramdisk.

So then I try to do the same thing with /dev

Code:

echo "Loading /dev to ramdisk"
mke2fs -q -I 1024 /dev/ram2 1024
mount /dev/ram2 /dev -o defaults,rw
cp -a /lib/dev /

Now the system will no longer boot. It get's though all the kernel stuff, but when it starts trying to work with the devices, the system hangs and I have to hit "oops" button on my computer.

I'm not sure if I'm doing this right, I got the instructions from some old documentation on creating a live CD that I tried to apply to what I'm doing. The tutorial recommended using devfs to load /dev into a ramdisk but I guess this is now obsolete.

Any suggestions?

Thanks!
...drkstr

**edit**
I rebooted to my ro test partition to try and get some usefull kernel mesages. Forgive me for paraphrazing, I didn't want to write down the entire demesg verbatim.

Code:

Uncompressing Kernel... OK booting
<bunch of kernel crap>
Ramdisk driver initialized: 16 Ram disks of 7777K size 1024 block size
<more kernel crap>
loop loaded (max 8 devices)
Warning: unable to open initial console
<just a little more crap then...>
SCSI0: SCSI host adapter emulation for IDE ATAPI devices
<Kernel dies!>

**edit again**
I forgot to mention that I'm using 2.4.31 kernel for the ro boot.

Daga · 07-15-2006, 12:55 PM

You might try manually creating the devices you need for your initrd image:

Code:

echo "    ** Device nodes..."
mknod initrd/dev/console c 5 1
mknod initrd/dev/null c 1 3
mknod initrd/dev/ram b 1 1
mknod initrd/dev/systty c 4 0
mknod initrd/dev/tty c 5 0

LOOP=63
while [ $LOOP -ge 0 ]; do
	mknod initrd/dev/tty$LOOP c 4 $LOOP
	let LOOP--
done

LOOP=255
while [ $LOOP -ge 0 ]; do
	mknod initrd/dev/loop$LOOP b 7 $LOOP
	let LOOP--
done

Also, I could be wrong, but using SCSI emulation for the CD-ROM drive isn't a bad thing -- and I think that is what the last kernel message you posted is about.

drkstr · 07-18-2006, 04:09 PM

Quote:

You might try manually creating the devices you need for your initrd image:

Thanks for the suggestion. I tried thinking this through a little more and realized I was going about it the wrong way. I was trying to use a ramdisk to bring my devices up, but I need the devices in order to use the ramdisk. I was finally able to get it working using an initrd method and using the apropriate options in my lilo.conf.

Quote:

Also, I could be wrong, but using SCSI emulation for the CD-ROM drive isn't a bad thing -- and I think that is what the last kernel message you posted is about.

I agree, this was just the last message I got before the system stopped booting.

Thanks again!
...drksr

Daga · 07-19-2006, 02:45 AM

Quote:

Originally Posted by drkstr

Thanks for the suggestion. I tried thinking this through a little more and realized I was going about it the wrong way. I was trying to use a ramdisk to bring my devices up, but I need the devices in order to use the ramdisk. I was finally able to get it working using an initrd method and using the apropriate options in my lilo.conf.

Hmmm, I think I was a little tired when I typed that. I neglected to say that it was part of my initrd creation script -- not the boot script

Hope everything is working!

drkstr · 07-19-2006, 02:56 AM

Quote:

Hmmm, I think I was a little tired when I typed that. I neglected to say that it was part of my initrd creation script -- not the boot script

Hope everything is working!

No problem, I was able to figure it out eventually. I copied the the basic devices you created in your script from /dev to /<initrd root>/dev before creating the initrd, and it seems to work OK. Your post got me thinking in the right direction at least.

best regards,
...drkstr