Read-only bind mounts not working properly

Question

Hello,
I discovered a strange behavior regarding mount --bind on my system. In the past I could create read-only bind mounts using first a mount --bind /source /dest and after that mount -o remount,ro /dest. But since some kernel update (not sure which) this procedure results in the complete filesystem of the source being remounted read-only, not only the /dest mountpoint. I also saw that bind-mounts are not shown as such in the outbput of mount:
the mountpoint was created using
mount --bind /mnt/data/Backup/vserver/Daten /mnt/data/homes/vserver/Daten
and results in the following output of mount:
/dev/mapper/data on /mnt/data/homes/vserver/Daten type ext4 (rw,noatime,nodiratime,user_xattr,acl,barrier=1,stripe=64,data=ordered)
so its reported as if i mounted the parent fs (/dev/mapper/data on /mnt/data) to the directory.
Does anyone know what caused this behavior, and how to get read-only bind-mounts back to a working condition?
Thanks in advance,
seiichiro0185

Answer 1

R00KIE wrote:
You could use the "alternative" way of doing it, which is exemplified in the manual page: '
mount --bind olddir newdir
mount -o remount,ro,bind olddir newdir
Here I can reproduce your problem but the "alternative" way seems to work fine.
That's not the alternative way, that's the only way. Though, you don't need to specify both the source and dest on the remount -- just the dest.
Last edited by falconindy (2012-01-31 13:32:12)