this post was submitted on 15 Mar 2024
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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 (andby-idshould 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 oldeth0,eth1, etc. could swap positions between Linux upgrades (or even between reboots) since they were also just the order the drivers were initialized in.I'm sure you know this, but to to supplement your comment for future readers, UUIDs are also a good solution for partitions.
Labels are better. IMO; they're semantic.
I agree. Also, I can swap a disk with a new one with the same label, no need to change fstab
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.
Right. I don't think they and I are in disagreement - just trying to help expand their statement. Thanks!
Right :) the original meme was just talking about drive names (/dev/sdX)
How are the uuids going to change unexpectedly?
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
ddin which case they won't change but they should, and you end up with duplicate UUIDs.Are UUIDs built into the hardware, or something your computer decides on based on the drive's serial number and shit?
Uuids are part of the gpt (table) on the disk.
You're thinking of
partuuid, regular uuids are part of the filesystem and made at mkfs timeAh. Makes sense.
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.
I could have RTFM but you guys are more fun.
Yeah, you get the best Linux info when reading meme comments 😁.
I tried a gentoo stage 2 or 3 like 20 years ago. I'm still good.
It's fun to have people around who read the friendly manual
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.
So if we swap drives about, the OS will see them as the same drive and/or partition?
Understood. Ty.
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.
Yeah, and ide only supported 4 drives at a time in most systems
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.
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?
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.
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.
The arch wiki lists some methods to permanently name network interfaces at https://wiki.archlinux.org/title/Network_configuration#Change_interface_name
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.
hardware-configuration.nix has entered the chat
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.