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I've had rsnapshot working under Slackware 13.0 for a few months. In my /etc/rsnapshot_<interval> scripts I first have it run is mount -o remount,rw then the very last thing it does is a mount -o remount,ro. The reason behind this is to protect my backups from accidental deletion by making them read-only whenever they are not actively being created.

When I upgraded to 13.1 this -o remount functionality seems to have either disappeared or broken:

# mount -t nfs
192.168.1.5:/slackware on /slackware type nfs (rw,addr=192.168.1.5)
# mount -o remount,ro /slackware
mount.nfs: an incorrect mount option was specified

Does anybody have a proposed solution to remedy this?

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I suspect mount.nfs doesn't support remounting. –  pjc50 Mar 31 '11 at 12:43
    
@pjc: not saying you're wrong but it did support it on Slackware 13.0. Why they would remove functionality on the next point release doesn't make much sense to me. –  SiegeX Mar 31 '11 at 15:58

1 Answer 1

This doesn't exactly answer your question, but I'd advise against using rsnapshot over NFS. You are negating the primary benefit of rsync which is the ability to transfer a small amount of data over the network to detect large portions of identical data. Rsync is designed to run over ssh where it can invoke an rsync server of the other side of the connection and communicate with it via it's own optimized protocol that uses a rolling checksum to identify identical data. When rsync is run over NFS and it thinks the file might be different due to timestamps or size, it must download the entire file over NFS even if it's only a small change since it has no way of querying the remote side for checksums across the data.

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