On Mon, Jun 23, 2008 at 05:25:58PM +0000, Helge Rohde wrote: > On Saturday 21 June 2008 22:47:31 Roland Smith wrote: > > On Sat, Jun 21, 2008 at 09:44:09PM +0000, Helge Rohde wrote: > > > Hello List, > > > > > > I need to write a backup script, and one of the required actions would be > > > a copy of the backup to an external firewire drive. I would like to make > > > this as easy as possible for the local staff, so i'd like to check > > > whether the drive is attached, if necessary mount it, copy over the > > > backup and unmount it again, so that the local staff can swap the > > > external disks when they're not used. > > > > > > Is there a canonical way to achieve what i want? I played with the idea > > > of simply checking for /dev/da0s1d's existance, but that won't disappear > > > on disconnect, so that would leave the is a possibility that although
Such devices should disappear on disconnect. > > > da0 is in /dev, it might not be connected. > > > > Use glabel(8) to give the device an unique label. There is no telling > > which device /dev/da0s1d is pointing to! After labeling you can check > > for /dev/<fstype>/<yourlabel>, which should be unique. Let me rephrase that. You should actually use the file system's utility to set a label. This works for UFS (newfs, tunefs), msdosfs (newfs_msdos), ISO9660 (mkisofs) and ntfs. > > Make sure to unmount the drive at the end of the backup script, or > > you'll get a kernel panic when staff pulls the plug on a mounted device. > > > > Roland > > Okay, it obviosly makes sense to use glabel instead of the device node. Will > the glabel appear/disappear depending on whether the drive is connected? Yes, just like regular device nodes. > Is it possible to have more then one physical drive with the same glabel(As i > plan to utilize two identical Firewire disks) ? You can label both drives the same. I don't know what will happen it you try to connect them both at the same time. I guess that the creation of the second label will fail. > Either way, i still need a way to check whether a drive is attached or not. Simple. Check for the device node. > Mounting( and unmounting!) will be done from the periodic backup > scripts. > > I am not sure how devd could help me with that, besides maybe write/delete a > zero-byte file somewhere and have the periodic script check for its > existence. It can't completely. It should be able to detect your labeled device and mount it somewhere. But you _have_ to unmount _before_ the device node disappears, lest you get the aforementioned panic. It's easier to have the backup script test if the labeled device node exists. Do not forget to print a message (after the script has unmounted the drive) for the operators that the backup is finished and that the device may be disconnected. > Thank you all for your help, You're welcome! Roland -- R.F.Smith http://www.xs4all.nl/~rsmith/ [plain text _non-HTML_ PGP/GnuPG encrypted/signed email much appreciated] pgp: 1A2B 477F 9970 BA3C 2914 B7CE 1277 EFB0 C321 A725 (KeyID: C321A725)
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