what does the error - readlink "//mnt/backup/path to file name" failed: Input/output error mean in the context of an rsync operation

What was the command you issued to do the rsync? It sounds like you are missing part of the location for where you are getting or putting the files. The command should look something like this:

rsync -vr --delete -e ssh ~/docs/ njk77@192.168.0.104:/home/nathan/docs/

the 1st ~/docs/ is the directory that you are copying FROM.
the 2nd /home/nathan/docs/ is the directory you are copying TO.

the njk77@192.168.0.104: is the location of the system to backup to.

I also happen to be using the ssh option to move files in this example.

Good luck, RSYNC is great!!!

I'm copying from one drive to another on the same machine so the command I use is:

rsync -av / /mnt/backup

but only get the above error on about 10 individual file pathnames, the rest seems to work ok in the few places I've checked.

It looks like you are copying your root directory. What files aren't working? Maybe they are wierd (ie just simlinks)?

well there doesn't seem to be any rhyme or reason to them

readlink "//mnt/backup/var/cache/samba/browse.dat" failed: Input/output error

is one, and the others are a couple of users excel files!!

First of all, why are you using rsync when copying to the same machine? Have you tried moving using the mv or cp command? If your trying to preserve ownership of the files, mv by default retains this and cp has options to do this. Use mv if you want to just move, use cp if you want to copy the files to the new location so they will be in two locations.

And if your trying to perform a backup of your whole system, probably best to use tar and gzip to make a backup to move to another destination.