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Tuesday, August 31, 2010

The most annoying error - cannot mount '/home': directory is not empty

Was working on migrating few SVM metadevice based filesystems to ZFS filesystem on Solaris 10 U8 and for the reason I have created ZFS filesystems with temporary mountpoint under /mnt like:

# zfs create –o mountpoint=/mnt/home –o quota=2g rpool/home

After creating this filesystem I’ll sync the data from metadevice based file system to ZFS based filesystem residing under /mnt like:

# rsync -axP --delete /home/ /mnt/home/

Once the data migrated I’ll un-mount the metadevice for /home and rearrange the mount point for ZFS filesystem back to /home using:

# zfs set mountpoint=/home rpool/home

While performing above command execution I get the error –

# zfs mount -a
cannot mount '/home': directory is not empty

This error may occur due to various reasons like one but not the last is auto mount daemon and so on which I’m not aware of… :)

I got the rid of this pesky issue performing “Overlay mount”

# zfs mount -O rpool/home

BTW then what is overlay mount? – Overlay mount allow the file system to be mounted over an existing mount point, making the underlying file system inaccessible. If a mount is attempted on a pre-existing mount point without setting this flag, the mount will fail, producing the error "device busy" or in ZFS terms “directory is not empty”.

This solution seems to be working just fine for me but I cannot guaranty that same will work for you as I said before there are various factors that leads to such issue.


Monday, August 9, 2010

alloc: /: file system full

Today I came across with a strange issue of file system full with error -

Aug 9 00:17:41 server1 ufs: [ID 845546 kern.notice] NOTICE: alloc: /: file system full

When I looked at the top disk space consumers I found nothing useful.

# df -h | sort -rnk 5

/dev/md/dsk/d0 3.0G 2.9G 0K 100% /
/dev/md/dsk/d3 2.0G 1.5G 404M 80% /var
/dev/md/dsk/d30 469M 330M 93M 79% /opt
/dev/md/dsk/d6 992M 717M 215M 77% /home
/dev/md/dsk/d33 752M 494M 198M 72% /usr/local/install

After doing a du on whole filesystem I can see it is showing 2.5G only and df showing 2.9G consumed space.

# du -shd /

I realized few days back I came across same issue on ZFS filesystem hosting oracle DB and below understanding helped me there.

Normally, If filesystem is full, then look around in the directories that will be hidden by mounted filesystems in higher init states or see if any files that are eating up the disk space, in case if you get nothing useful from this exercise then one of the things to check is the open files and consider what has been cleaned up. Sometimes, if an open file is emptied or unlinked from the directory tree the disk space is not de-allocated until the owning process has been terminated or restarted. The result is an unexplainable loss of disk space. If this is the cause a reboot would clear it up. If you can't reboot consider any process that would be logging to that partition as a suspect and check all of your logs for any entries that imply rapid errors in a process.

In my case, reboot was not possible as the server caused file system full

# lsof +aL1 /

lsof: WARNING: access /.lsof_server1: No such file or directory
lsof: WARNING: created device cache file: /.lsof_server1
lsof: WARNING: can't write to /.lsof_server1: No space left on device
scp 16472 root 4r VREG 85,0 238616064 0 119696 / (/dev/md/dsk/d0)
scp 22154 root 4r VREG 85,0 238213120 0 119677 / (/dev/md/dsk/d0)


``+L1'' will select open files that have been unlinked. A specification of the form ``+aL1 '' will select unlinked open files on the specified file system.

I got the processes ID's via lsof, after verifying the processes I killed them and suddenly it has released ~450MB space.

# df -kh | sort -rnk 5
/dev/md/dsk/d0 3.0G 2.5G 418M 86% /
/dev/md/dsk/d3 2.0G 1.5G 406M 80% /var
/dev/md/dsk/d30 469M 331M 91M 79% /opt
/dev/md/dsk/d6 992M 717M 215M 77% /home
/dev/md/dsk/d33 752M 494M 198M 72% /usr/local/install

Hope this helps.