unmounting a filesystem mounted by /init (initramfs)

unmounting a filesystem mounted by /init (initramfs)

[Rafael Espíndola]

I am trying to build a system that uses a unionfs as root. The init
script is based on the one used by gentoo and uses initramfs. The
problem is how to remount the unionfs constituents read only during
halt.

cat /proc/mounts displays /dev/hda1 (ext2) mounted rw in /memory. The
problem is that /memory is no longer visible after the init script did
a chroot and a

mount -o remount,ro /dev/hda1

says that /dev/hda1 is not mounted!

does any anyone has an idea?

Thanks,
Rafael

Re: unmounting a filesystem mounted by /init (initramfs)

[Denis Vlasenko]

On Friday 29 July 2005 01:49, you wrote:
> I am trying to build a system that uses a unionfs as root. The init
> script is based on the one used by gentoo and uses initramfs. The
> problem is how to remount the unionfs constituents read only during
> halt.
> 
> cat /proc/mounts displays /dev/hda1 (ext2) mounted rw in /memory. The
> problem is that /memory is no longer visible after the init script did
> a chroot and a

"A chroot"? Better provide exact sequence of mounts, chroots which you
execute. Otherwise people need to guess.
 
> mount -o remount,ro /dev/hda1
> 
> says that /dev/hda1 is not mounted!
> 
> does any anyone has an idea?

Use lazy umount (umount -l) while fs is still visible
--
vda

Re: unmounting a filesystem mounted by /init (initramfs)

[Rafael Ávila de Espíndola]

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On Friday 29 July 2005 02:34, Denis Vlasenko wrote:
> "A chroot"? Better provide exact sequence of mounts, chroots which you
> execute. Otherwise people need to guess.
The relevant commands are:

mount -t ext2 /dev/hda1 /memory
mount -t unionfs -o dirs=/memory /union
mount -t squashfs /dev/hda2 /newroot
unionctl /union --add --after 0 --mode ro /newroot
chroot /union /sbin/init

The most promissing Idea I had till now is to move the ext2 mount and the 
unionctl past the point were /sbin/rc runs udevstart. I will try it as soon 
as possible.

> Use lazy umount (umount -l) while fs is still visible
The busybox umount doesn't support lazy unmount :(
Anyway, I don't think that this would work since the unionfs will be using the 
ext2 partition to the very end and there won't be a chance to unmount it.

> vda
Thank you very much,
Rafael

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Re: unmounting a filesystem mounted by /init (initramfs)

[Rafael Ávila de Espíndola]

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> Use lazy umount (umount -l) while fs is still visible
This works after all :)

I was I bit confused on how to remove the ext2 from the union but manage to do 
it. Then it was a simple matter of implementing lazy unmount in busybox.

Thank you very much,
Rafael

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