mount -o remount,ro cause error "device is busy"

hi, all;
I have upgraded my kernel to version 2.4.
And i have tested 2.4.16 and 2.4.18. Both of these two version have the same problem when system reboot. "/: device is busy";
in shutdown script:
umount -a
mount -n -o ro,remount /
these two line result error: device is busy.

I switch to init 1, and all user process go away.
except the following:

root         1  0.1  0.7  1056  484 ?        S    15:46   0:04 init [S] 
root         2  0.0  0.0     0    0 ?        SW   15:46   0:00 [keventd]
root         3  0.0  0.0     0    0 ?        SWN  15:46   0:00 [ksoftirqd_CPU0]
root         4  0.0  0.0     0    0 ?        SW   15:46   0:00 [kswapd]
root         5  0.0  0.0     0    0 ?        SW   15:46   0:00 [bdflush]
root         6  0.0  0.0     0    0 ?        SW   15:46   0:00 [kupdated]
root      1042  0.0  0.7  1056  484 tty1     S    16:33   0:00 init [S] 
root      1043  0.6  1.5  1840 1004 tty1     S    16:33   0:00 /bin/sh
root      1045  0.0  1.0  2260  680 tty1     R    16:33   0:00 ps aux

then i try
mount -o ro,remount /
error occurs: device is busy.

and i try
mount -o ro,remount /usr
(another partition)
also error occurs: device is busy.

but when i try umount /usr,
it works.

certainly, there is error
device is busy for command umount /.

How can i resolve this problem?

Regards;
Michael

We need more info about your config. Do you have any patches in this kernel? What modules have been loaded? Highmem? x86? drive controller? drive? ram size? lspci output, etc...

I haven't apply any patch on my 2.4.16 kernel. But when i test 2.4.18, i apply many netfilter patch in iptables 1.2.5 via patch-o-matics..
like newnat,ip_nat_h323, iplimit and so on.

I attach my config file for 2.4.18 in this mail.

Regards
Michael

Michael Cheung <[email protected]> writes:

|> hi,
|> 
|> maybe i am wrong, but I really can't find any other process runing.
|> 
|> my step is:
|> 1) "/" and "/usr" are busy
|> 2) shut down to single user mode
|> 3) "/" still busy
|> 4) "/usr" can be unmounted, but can't mount -o ro,remount /usr, show busy error.
|> 5) umount -a, after this, only /proc and / exist.
|> 6) mount -o ro,remount /, show busy error.
|> 
|> I have mentioned I have used "ps aux" to check the process list,
|> there are no user process left. except the following: (repost)
|> root         1  0.1  0.7  1056  484 ?        S    15:46   0:04 init [S] 
|> root         2  0.0  0.0     0    0 ?        SW   15:46   0:00 [keventd]
|> root         3  0.0  0.0     0    0 ?        SWN  15:46   0:00 [ksoftirqd_CPU0]
|> root         4  0.0  0.0     0    0 ?        SW   15:46   0:00 [kswapd]
|> root         5  0.0  0.0     0    0 ?        SW   15:46   0:00 [bdflush]
|> root         6  0.0  0.0     0    0 ?        SW   15:46   0:00 [kupdated]
|> root      1042  0.0  0.7  1056  484 tty1     S    16:33   0:00 init [S] 
|> root      1043  0.6  1.5  1840 1004 tty1     S    16:33   0:00 /bin/sh
|> root      1045  0.0  1.0  2260  680 tty1     R    16:33   0:00 ps aux
|> 
|> and I also checked by fuser -v /usr,
|> only used by kernel.
|> and fuser -c /, show many process list above.
|> 
|> If i have a mistake, would you like to tell me where is the mistake?

Check for references to deleted files (/proc/*/fd). "init u" should help.

Andreas.

Andreas Schwab, SuSE Labs, [email protected]
SuSE GmbH, Deutschherrnstr. 15-19, D-90429 Nürnberg
Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

^^^^
Best bet is to man lsof.

lsof's your buddy.

Share and Enjoy. 

Please don't send that. It clearly appears to be a user problem. Order of operations, as I read in the original email:
1) "/" and "/usr" are busy
2) shut down to single user mode
3) "/" still busy
4) "/usr" can be unmounted
5) didn't check that root can be remounted after umounting "/usr"

Clearly, some program is keeping "/usr" busy (which is keeping "/" busy) before the change to single user mode. Just a bit of "lsof" needed to find such things.

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/

hi,

maybe i am wrong, but I really can't find any other process runing.

my step is:
1) "/" and "/usr" are busy
2) shut down to single user mode
3) "/" still busy
4) "/usr" can be unmounted, but can't mount -o ro,remount /usr, show busy error.
5) umount -a, after this, only /proc and / exist.
6) mount -o ro,remount /, show busy error.

I have mentioned I have used "ps aux" to check the process list, there are no user process left. except the following: (repost)

root         1  0.1  0.7  1056  484 ?        S    15:46   0:04 init [S] 
root         2  0.0  0.0     0    0 ?        SW   15:46   0:00 [keventd]
root         3  0.0  0.0     0    0 ?        SWN  15:46   0:00 [ksoftirqd_CPU0]
root         4  0.0  0.0     0    0 ?        SW   15:46   0:00 [kswapd]
root         5  0.0  0.0     0    0 ?        SW   15:46   0:00 [bdflush]
root         6  0.0  0.0     0    0 ?        SW   15:46   0:00 [kupdated]
root      1042  0.0  0.7  1056  484 tty1     S    16:33   0:00 init [S] 
root      1043  0.6  1.5  1840 1004 tty1     S    16:33   0:00 /bin/sh
root      1045  0.0  1.0  2260  680 tty1     R    16:33   0:00 ps aux

and I also checked by fuser -v /usr,
only used by kernel.
and fuser -c /, show many process list above.

If i have a mistake, would you like to tell me where is the mistake?

thanks.

Regards;
Michael