On Tue, 2010-02-02 at 22:07 +1100, david wrote: > Does fstab allow for two UUID's having the same mount point thus: > > > UUID=2e7c5578-933a-4b09-a89d-14b6be718fe5 /mnt/BACKUP ext4 defaults 0 0 > UUID=b007bc41-0280-48d5-b958-9160092e3d44 /mnt/BACKUP ext4 defaults 0 0
Yes. Have you tried it yet? :-) > Especially given that this machine has three caddies on board, so it's > theoretically possible for me to accidentally mount both backup drives > simultaneously! Would I be so silly? it's at least possible. > > Does anyone know what happens if they both successfully mount? Anecdote time! One of the sites I look after runs a large proprietary application server, and the customer's installed SOE uses a /tmp partition far too small for the installation / upgrade process utilised by said application server. The installer also has this wonderful bug wherein it ignores all attempts to define a new temporary file location. My process for applying hotfixes to the app server includes: Create a large empty file under /var/tmp . Create a filesystem in this file. Mount it over the existing /tmp using the loopback driver. Run the upgrade. Unmount the temporary /tmp . Say you have the first filesystem mounted on /mnt/BACKUP , and some processes have open file handles on that first filesystem. Mounting a second filesystem over /mnt/BACKUP will not interrupt those open file handles - all reading and writing using those handles will still use the first filesystem. I *think* that new file handles opened by those old processes will use the second filesystem (including readdir() calls and the like), but I haven't tested this too thoroughly. New processes attempting to read from /mnt/BACKUP will only see the second filesystem mounted there. Listing the mounted filesystems with the mount command will show two filesystems mounted on /mnt/BACKUP . I have no idea what will happen when you just run "umount /mnt/BACKUP", and would suggest being more explicit about which filesystem you want to unmount. Bottom line, though, is that you won't break anything by experimenting with this. If you're nervous, make sure you have a backup of the filesystems you're playing with, or create a couple of loopback ones to test with. Also, I can't wait until the end of this month, when those app servers are retired... -- Pete -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
