/dev/sd disk blockdevices randomly ordered at every boot

[TCH]

I've been using Devuan 2 for 4 years and it consistently detected my drives as this:
/dev/sda: primary SSD where the system resides
/dev/sdb: secondary SSD where i back up the system with rsync regularly
/dev/sdc: secondary HDD where i back up the data with rsync regularly
/dev/sdd: primary HDD where the data resides
This order was constant, it never changed. This is the same order as the disks are plugged into the motherboard. Clean, obvious, logical. Working.

A few days ago i've upgraded to Devuan 4 and now the order is entirely random. At every boot.
I tried to check how can i set up a persistent order, but all i found is how to write fstab entries by disk id; but this is not a partition problem, it is a disk blockdevice detecting order problem, it cannot be solved from fstab.

Any tips on this?

[bsd-keith]

Drives get labelled as they get found by the O/S on boot up, normally, you use labels or UUID in fstab to mount them at certain points on the filesystem - I don't think it is possible to make them be found in a specific order.

[Head_on_a_Stick]

Originally Posted by TCH

I tried to check how can i set up a persistent order, but all i found is how to write fstab entries by disk id; but this is not a partition problem, it is a disk blockdevice detecting order problem, it cannot be solved from fstab.

It is not a "problem" at all. It is the expected behaviour, as bsd-keith notes.

The block devices are assigned by (e)udev asynchronously so a specific order cannot be guaranteed. I am very surprised that the devices were consistently ordered under Devuan ASCII, that is unusual.

Just use UUIDs, LABELs, PARTUUIDs[1] or PARTLABELs[1] in /etc/fstab, that is the recommended approach.

[1] Only for disks with a GUID partition table.

[TCH]

Guys, you did not get it: this has nothing to do with partitions and fstab; i need the blockdevices in this order!

[Head_on_a_Stick]

That is not possible. Why do you think you "need" the devices in that order? Why does editing /etc/fstab and substituting UUID=$uuid not solve your problem?

[TCH]

Because this has nothing to do with fstab, as i said twice already. I don't even use fstab for backup.

I have a script which mounts the partitions of the two SSD-s and the two HDD-s and rsyncs the alive system and data to the backup ones.
Sure, i could do mounting by UUID-s, but if the partition table is changed, because i rearrange/resize/format them (this happened in the past several time), then the UUIDs are changed and i need to modify the script to change the wired in UUID-s. The same applies for disklabels. As for /dev/disk/by-id/ that only works, until i need to change one of the disks again. (Once one of my backup HDD-s became faulty. No data loss, but the device was needed to be replaced.)

The only method which worked for years is the blockdevices detected by the order of how they are plugged into the motherboard. During that time and with that method it did not matter what changed in the partition table or what device got replaced.

Are you 100% sure, that it is imposible? Because now, that i recall, it was not Devuan 2 only which did it. Debian 8 also did the same for 4 years. Debian 7 for half a year. And Ubuntu 10.04 for 2 years (but without SSD-s).

[Head_on_a_Stick]

Originally Posted by TCH

Sure, i could do mounting by UUID-s, but if the partition table is changed, because i rearrange/resize/format them (this happened in the past several time), then the UUIDs are changed

I think the PARTUUID would be consistent in that case. Needs a GPT disk though but you should be using that anyway because MS-DOS ("MBR" type) partition tables are inferior.

The same PARTUUID can be recreated if you swap a new drive in:
https://bbs.archlinux.org/viewtopic.php?id=215541

Originally Posted by TCH

Are you 100% sure, that it is imposible?

Yes but I'm not an expert. Perhaps somebody here will correct me.

[TCH]

Originally Posted by Head_on_a_Stick

I think the PARTUUID would be consistent in that case.

If a partition is removed, or a device is replaced, it is the same.

Originally Posted by Head_on_a_Stick

Needs a GPT disk though but you should be using that anyway because MS-DOS ("MBR" type) partition tables are inferior.

I agree, but unfortunately my SSD-s use the MBR type. Cannot remember why, but IIRC i tried some BSD-s and they did not know the GPT type, just the BSD and MBR.

Originally Posted by Head_on_a_Stick

The same PARTUUID can be recreated if you swap a new drive in:
https://bbs.archlinux.org/viewtopic.php?id=215541

Thanks, but if i have to change things after modification anyway, then it is more easier to simply change the UUID-s in the script...

[TCH]

In the end, partition labels was chosen for solution: https://dev1galaxy.org/viewtopic.php?id=5508#p40687