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[Solved] Assign specific device ID to USB external disk
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solamour
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PostPosted: Fri Nov 16, 2012 6:09 pm    Post subject: [Solved] Assign specific device ID to USB external disk Reply with quote

I have 2 USB external disks: Seagate and WD.

Code:
$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 125: ID 1058:1021 Western Digital Technologies, Inc. Elements 2TB
Bus 001 Device 013: ID 0bc2:3320 Seagate RSS LLC


Seagate was plugged in first, so it is recognized as /dev/sdb, while WD is /dev/sdc. The problem is, whenever I reboot, depending on which one gets recognized first, the drive IDs get switched (i.e. WD gets /dev/sdb, and Seagate gets /dev/sdc), and that messes up my backup scripts.

How do I always assign /dev/sdb to Seagate no matter which one gets plugged first? I think it has something to do with udev rules (because that's how network adapters are done), but I'm not sure how to proceed from here. I'd appreciate any suggestions.
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sol


Last edited by solamour on Sun Nov 18, 2012 5:34 am; edited 1 time in total
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gabrielg
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Joined: 16 Nov 2012
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PostPosted: Fri Nov 16, 2012 6:22 pm    Post subject: Reply with quote

I believe that you can play with udev's rules, but I never tried it.

I'm not sure what your problem is, but what I do to overcome the order in which external drives are selected is by using labels (tune2fs /dev/partition -L nameoflabel) and then using that in /etc/fstab, for example:
Code:

LABEL=nameoflabel       /path/to/mountpoint       ext4        [your options]    0   0


All this, assuming you use ext4, perhaps it works with vfat and friends, haven't tried it.
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solamour
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PostPosted: Fri Nov 16, 2012 6:30 pm    Post subject: Reply with quote

Use the label of the disk... clever. Will try. Thanks.
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sol
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blakdeath
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PostPosted: Fri Nov 16, 2012 6:33 pm    Post subject: Reply with quote

well as gabriel said you can use the label, you can also use the UUID of the media
I don't know the exact commands for managing the whole uuid thingie, but i suppose this would be helpful:
http://www.gentoo-wiki.info/Gentoo:/dev/disk/by-uuid
there's an fstab entry example here: http://linux.byexamples.com/archives/321/fstab-with-uuid/
labels are just easier though
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solamour
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Joined: 21 Dec 2004
Posts: 508
Location: San Diego, CA

PostPosted: Sun Nov 18, 2012 5:33 am    Post subject: Reply with quote

After trying a few different methods,

1) Use the label of the disk.
2) Add "udev" entry (https://wiki.archlinux.org/index.php/Map_Custom_Device_Entries_with_udev).
3) Use UUID in /etc/fstab.

I ended up with the UUID method. No particular reason, and other methods worked equally well. Thank you everyone for taking time to share your suggestions.
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sol
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