I have been using rsync over ssh (cygwin) for some time now from a Windows 2003 Server to back up files to a Debian box which has a USB hard drive attached.
The files are rsynced directly to the USB hard drive which is mounted as /media/backup on the Debian box.
The backup is run from a scheduled task on the Windows box and the stdout and stderr are output to files which are emailed to me after the backup completes.
Every now and again I see errors in the stderr file like:
rsync: failed to set times on "/media/backup/[some file name] ": Read-only file system (30)
for every file that has changed since the last backup.
When I see this error I unmount the drive and remount. That resolves the problem.
Can anyone enlighten me as to why this error occurs? i.e. Why would a USB drive become read-only once every couple of months?