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velis
Asked: 2017-11-17 04:31:14 +0800 CST

How can I instruct ubuntu to map drives to specific /dev/xxx

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This is a reverse question to tons of questions about how to identify which physical drive matches /dev/sdx. I want to avoid having to ask that question when a drive fails.

I have bought an adapter capable of serving 8 drives (9211-8i). Both SFF-8087 cables are nicely marked so that I know which physical drive is which.

However, the attached drives are mapped as /dev/sdx

Just for reference, my M.2 boot drive nicely mounts as /dev/nvmxxx which nicely distinguishes it from the other drives in the system.

So, how can I instruct ubuntu device mapper to map my controller attached drives as something distinct & EXACTLY matching the physical port a drive is attached to, e.g. /dev/scsi[abcdefgh]? In fact, I'd even prefer numeric port numbers, but I'm not sure it matches unix mapping rules where drives are marked with letters, then followed by partition numbers, e.g. /dev/sda -> /dev/sda1

Thanks

hard-drive

1 Answers

  1. Best Answer

    Have a look at /dev/disk/by-path/, which essentially does this. The other way is to reference it by UUID or Label, which is a property of the partition, and not the hardware. If you reference disks by UUID, this will not change, even if you move the drive to a different computer.

    $ ls /dev/disk/
by-id  by-label  by-path  by-uuid

$ ls /dev/disk/by-path/
pci-0000:03:00.0-scsi-0:0:0:0        pci-0000:03:00.0-scsi-0:0:0:0-part2
pci-0000:03:00.0-scsi-0:0:0:0-part1  pci-0000:03:00.0-scsi-0:0:0:0-part5

    As you can see, this uniquely identifies the drive depending on path, including bus connection. These files are a symlink to the actual device:

    $ ls -la pci-0000\:03\:00.0-scsi-0\:0\:0\:0
lrwxrwxrwx 1 root root 9 Oct 18 09:08 pci-0000:03:00.0-scsi-0:0:0:0 -> ../../sda

    To identify a drive, the utility lsblk is useful:

    lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
fd0      2:0    1    4K  0 disk
sda      8:0    0    8G  0 disk
├─sda1   8:1    0  7.6G  0 part /
├─sda2   8:2    0    1K  0 part
└─sda5   8:5    0  383M  0 part [SWAP]
sr0     11:0    1  247M  0 rom

    To see the UUID of a disk, you can run sudo lsblk -f. This will show the UUID, which you will find in /dev/disk/by-uuid/ as well:

    $ sudo lsblk -f
[...]
    └─system-swap  swap          73195006-1ae6-4d5f-87df-78cb52f48f15   [SWAP]
$ ls -la /dev/disk/by-uuid/73195006-1ae6-4d5f-87df-78cb52f48f15
    lrwxrwxrwx 1 root root 10 Oct 20 17:33 /dev/disk/by-uuid/73195006-1ae6-4d5f-87df-78cb52f48f15 -> ../../dm-3

    This can also be used in fstab. For instance:

    UUID=f0a2eebe-1791-4c44-ab86-75ea81a82c43 /boot ext4 acl,user_xattr 1 2

    will mount the partition with that UUID on /boot.

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