Re: pivot_root. unmount old root
What I still need to figure out is how I can replace init with a custom process... but I think for that I will have to patch init itself. Why do you need to patch init? I'm not sure if I really have to but I don't want to run all init scripts of the new system right away but do some other stuff. Would be nice to put the whole system back into the state of the early initramfs phase. But perhaps some workaround with init is sufficient. I'll do some research on that topic. Thx, for your help with the pivot_root issue! K. Haselhorst -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4bac7564.90...@mathematik.uni-marburg.de
Re: pivot_root. unmount old root
Hello, Maybe it's time to step back and ask a more basic question. What is it that you are trying to accomplish? I know that you are trying to do a pivot_root. But *why* are you trying to do a pivot_root? Why do you think you need to do it? What is the real-world problem that you are trying to solve? I want to go back into an initramfs setting so that only the running kernel and one specific process remains. Goal is to be able to boot a new system from there with a new hard drive (for example mounted via nfs or some other way) withouth the need to reboot the entire kernel. The whole thing is running within a xen domU atm. So the new hard disk could be passed through via xend or mounted via nfs. And for cleanly terminating the first system I need to unmount the root filesystem and somehow replace the old init process with my specific process running in that initramfs setting. According to the pivot_root manpage, it should be possible to clear all dependencies to the old root fs so that it can be unmounted after the pivot_root command. And that's what not working for me. K. Haselhorst -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4ba7bf1e.1020...@mathematik.uni-marburg.de
Re: pivot_root. unmount old root
You would probably want to run all the executable files in /etc/rc6.d
in alphabetical order, supplying the stop parameter, with the
exception of the last one, which on my system is S90reboot.
that's what I was doing - only with runlevel 0 without doing the actual
halt at the end.
Then run something like this:
--
#!/bin/sh
# Example: mount the new root file system over NFS from 10.0.0.1:/my_root
# and run init.
ifconfig lo 127.0.0.1 up # for portmap
# configure Ethernet or such
portmap # for lockd (implicitly started by mount)
mount -o ro 10.0.0.1:/my_root /mnt
killall portmap # portmap keeps old root busy
cd /mnt
pivot_root . old_root
exec chroot . sh -c 'umount /old_root; exec /sbin/init \
dev/consoledev/console 21
--
I only see 2 places (without patching init itself) to put these commands:
1. into a new shutdown script in place of S90{halt,reboot}
2. into the rc script
But no matter which of these I choose there remains at least init and
perhaps the process executing rc running and keeping the old root busy.
So I cannot unmount it. At least on my system init has opened some
shared libraries in old-root/lib/... and rc as well (if it is still running)
The same would happen if I restarted init with telinit -u runlevel...
Your script above is from the manpage of pivot_root, isn't it? I really
wonder in which context this example (and also the other one given in
the manpage) could work? Have you sucessfully tried it on your system?
K. Haselhorst
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Re: pivot_root. unmount old root
Hello, fuser -m /home will list the process ids which are accessing any file under /home. Compare that to the output of ps aux to see which processes you need to terminate in order to be able to umount /home. Since I'm doing a pivot_root before trying to umount the old root there are still several processes keeping some files open inside the old root subdirs. Init is still running, als well as rc and one shutdown script (atm I'm doing the pivot_root just before shutdown, because most processes are terminted by the time). If I kill one of these processes, the systems gets shut down. I don't understand why there is still that shutdown script running, because I'm doing a exec chroot. The pivot_root's manual says: Note that exec chroot changes the running executable, which is necessary if the old root directory should be unmounted afterwards. And the init process is always running, so how does pivot_root handle the open files of init? I did move the /proc and /dev mountpoints from old-root to the new root - might that cause some problems? If I don't do that - lsof or fuser of course don't show any open files for old-root, but I'm not able to unmount to old-root either. K. Haselhorst -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4ba62144.9050...@mathematik.uni-marburg.de
pivot_root. unmount old root
Hello, I'm running debian lenny with xen kernel 2.6.26, amd64. Inside a domU I need to make a pivot_root and unmount the old root afterwards. I've done the following: cd /newroot (newroot contains a minimal system from initrd, dev/console, dev/null and old-root are available unter newroot/) exec dev/console dev/console 21 pivot_root . old-root exec chroot . bin/sh umount -n old-root but I always get: device is busy - so I can't umount the old root. /proc/mounts shows that the proc fs is still mounten under old-root/proc and an umount old-root/proc doesn't work either (device is busy, too). I also tried to umount proc before doing the pivot_root, but no luck either. Why doesn't pivot_root remove the proc mountpoint from old-root? As I understand the documentation - it should clear all dependencies so that the old-root can be unmounted afterwards... Any ideas or suggestions to help would be great! K. Haselhorst -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4ba4a71f.8060...@mathematik.uni-marburg.de
Re: pivot_root. unmount old root
no, I don't have X. I just tried to mount --move /dev and /proc to the new root before actually doing the pivot-root. proc/mounts doesn't show any mountpoints under old-root afterwards, but an umount still gives device busy... On 03/20/2010 02:33 PM, Rogerio Luz Coelho wrote: are you doing this with X enabled? If so stop X before atempting a umount Rogerio 2010/3/20 Katharina Haselhorst bran...@mathematik.uni-marburg.de mailto:bran...@mathematik.uni-marburg.de Hello, I'm running debian lenny with xen kernel 2.6.26, amd64. Inside a domU I need to make a pivot_root and unmount the old root afterwards. I've done the following: cd /newroot (newroot contains a minimal system from initrd, dev/console, dev/null and old-root are available unter newroot/) exec dev/console dev/console 21 pivot_root . old-root exec chroot . bin/sh umount -n old-root but I always get: device is busy - so I can't umount the old root. /proc/mounts shows that the proc fs is still mounten under old-root/proc and an umount old-root/proc doesn't work either (device is busy, too). I also tried to umount proc before doing the pivot_root, but no luck either. Why doesn't pivot_root remove the proc mountpoint from old-root? As I understand the documentation - it should clear all dependencies so that the old-root can be unmounted afterwards... Any ideas or suggestions to help would be great! K. Haselhorst -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org mailto:debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org mailto:listmas...@lists.debian.org Archive: http://lists.debian.org/4ba4a71f.8060...@mathematik.uni-marburg.de -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4ba4ed31.2040...@mathematik.uni-marburg.de
