this post was submitted on 15 Mar 2024
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    Yeah yeah, we know you're special (lemmy.dbzer0.com)
    submitted 10 months ago by [email protected] to c/[email protected]
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    [–] [email protected] 175 points 10 months ago* (last edited 10 months ago) (6 children)

    and you shouldn't be using any of those, since the order can and will change. The numbers are based on the order the devices and device drivers are initialized in, not based on physical location in the system. The modern approach (assuming you're using udev) is to use the symlinks in /dev/disk/by-id/ or /dev/disk/by-uuid/ instead, since both are consistent across reboots (and by-id should be consistent across reinstalls, assuming the same partitioning scheme on the same physical drives)

    This is also why Ethernet devices now have names like enp0s3 - the numbers are based on physical location on the bus. The old eth0, eth1, etc. could swap positions between Linux upgrades (or even between reboots) since they were also just the order the drivers were initialized in.

    [–] [email protected] 45 points 10 months ago (2 children)

    I'm sure you know this, but to to supplement your comment for future readers, UUIDs are also a good solution for partitions.

    [–] [email protected] 10 points 10 months ago (1 children)

    Labels are better. IMO; they're semantic.

    [–] [email protected] 4 points 10 months ago

    I agree. Also, I can swap a disk with a new one with the same label, no need to change fstab

    [–] [email protected] 8 points 10 months ago (3 children)

    I think OP's point was that UUIDs can still change, but the stuff that makes up the /by-id/ names cannot. Granted, those aren't applicable to partitions.

    [–] [email protected] 4 points 10 months ago* (last edited 10 months ago)

    Right. I don't think they and I are in disagreement - just trying to help expand their statement. Thanks!

    [–] [email protected] 3 points 10 months ago

    Right :) the original meme was just talking about drive names (/dev/sdX)

    [–] [email protected] 1 points 10 months ago (1 children)

    How are the uuids going to change unexpectedly?

    [–] [email protected] 2 points 10 months ago

    Depends on your definition of "unexpected". OP was talking about reinstalls for example, where the root partition is deleted and recreated and its UUID will change as a result. If you copy an fstab from an older system backup you will fail the mount the root partition.

    UUIDs can also cause some reverse trouble if you clone them with dd in which case they won't change but they should, and you end up with duplicate UUIDs.

    [–] PsychedSy 17 points 10 months ago (3 children)

    Are UUIDs built into the hardware, or something your computer decides on based on the drive's serial number and shit?

    [–] [email protected] 33 points 10 months ago (2 children)

    Uuids are part of the gpt (table) on the disk.

    [–] [email protected] 10 points 10 months ago

    You're thinking of partuuid, regular uuids are part of the filesystem and made at mkfs time

    [–] PsychedSy 3 points 10 months ago

    Ah. Makes sense.

    [–] [email protected] 29 points 10 months ago (1 children)

    According to Arch Wiki they get generated and stored in the partition when it is formatted. So kinda like labels but automated and with (virtually) no collision risk.

    [–] PsychedSy 10 points 10 months ago (2 children)

    I could have RTFM but you guys are more fun.

    [–] [email protected] 5 points 10 months ago (1 children)

    Yeah, you get the best Linux info when reading meme comments 😁.

    [–] PsychedSy 2 points 10 months ago

    I tried a gentoo stage 2 or 3 like 20 years ago. I'm still good.

    [–] [email protected] 4 points 10 months ago

    It's fun to have people around who read the friendly manual

    [–] [email protected] 6 points 10 months ago (1 children)

    No. Since each partition gets its own UUID, it means it's generated by the OS on creation, no matter the number of partitions. On boot kernel will scan all UUIDs and then mount and map according to them, which is sightly less efficient method than naming block device directly, but far easier for humans and allows you to throw your drives to whichever port you like.

    [–] PsychedSy 1 points 10 months ago (1 children)

    So if we swap drives about, the OS will see them as the same drive and/or partition?

    [–] [email protected] 15 points 10 months ago* (last edited 10 months ago) (1 children)

    Back in my day, /dev/hda was the primary master, hdb was the primary slave, hdc was the secondary master and hdd was the secondary slave.

    Nothing ever changed between reboots. Primary/secondary depended on which port the ribbon cable connected to on the motherboard, and ~~primary/secondary~~ master/slave was configured by a jumper on the drive itself.

    [–] [email protected] 5 points 10 months ago (1 children)

    Yeah, and ide only supported 4 drives at a time in most systems

    [–] [email protected] 1 points 10 months ago* (last edited 10 months ago)

    If you had a Sound Blaster 16, you had an extra IDE port on the board, which DOS couldn't see and you had to load special drivers to use them. Usually it was used for the CD-ROM.

    [–] [email protected] 11 points 10 months ago (3 children)

    I have a hatred for the enp id thing as it isn't any better for me. It changes on me every time I add/remove a hard drive or enable/disable the WiFi card in the BIOS. For someone who is building up a server and making changes to it, this becomes a real pain. What happens if a drive dies? Do I have to change the network config yet again over this?

    [–] [email protected] 7 points 10 months ago* (last edited 10 months ago) (1 children)

    How is that happening? The number on the bus shouldn't change from adding or removing drives. I could imagine this with disabling a card in UEFI / BIOS if that basically stops reporting the bus entry completely. But drives?

    Anyhow, if I'm not mistaken, you can assign a fixed name based on the reported MAC.

    [–] [email protected] 3 points 10 months ago* (last edited 10 months ago) (1 children)

    It is only the nvme drives that do it. That damn PCI busses and iommu groups get renumbered every damn time I remove or add one. The SATA is safe though.

    [–] [email protected] 4 points 10 months ago

    The arch wiki lists some methods to permanently name network interfaces at https://wiki.archlinux.org/title/Network_configuration#Change_interface_name

    [–] [email protected] 4 points 10 months ago* (last edited 10 months ago)

    Use a systems rule to give it a consistent name based on its MAC address, driver, etc. I just had this exact same problem setting up my servers.

    root@prox1:~# cat /etc/systemd/network/10-persistent-10g.link 
[Match]
Driver=atlantic

[Link]
Name=nic10g

root@prox1:~# cat /etc/systemd/network/10-persistent-1g.link 
[Match]
Driver=igb

[Link]
Name=nic1g
    [–] [email protected] 4 points 10 months ago

    hardware-configuration.nix has entered the chat

    [–] [email protected] 3 points 10 months ago

    Having used gentoo for quite some time, there have been several occations where my network broke because the changing names and naming conventions of the network interfaces.