Can someone give a basic description of how linux assigns drive letters?

I understand that a drive letter assignment is not static. If I add a drive between /dev/sda and /dev/sdb, my /dev/sdb will become /dev/sdc and the new drive will become /dev/sdb.

I have a hot swap tray and have come into some unexpected behavior. I removed /dev/sde from the hot swap tray and then loaded another drive into this same tray. When I mounted the new drive with options in fstab, it wouldn't mount because the new drive was /dev/sdf, not /dev/sde. Apparently, linux is looking at the id of the drive in addition to it's place in the BIOS chain.

My fstab entry is:
/dev/sde /backups auto noauto,rw,noexec,async,user 0 0

I was avoiding using UUIDs in the fstab so that new HDDs would not have to be "registered" in the fstab prior to use.

Is there a way to tell linux (or fstab) whatever drive is plugged into SATA channel X mount to /mountpoint?

Thanks,
WT

udev. Writing udev rules is slightly outdated (the udevadm command has replaced some of the commands shown) but is the best guide I know of.

I'm answering my own questions so others know the answer:

udev is not necessary.

tree /dev/disk will list not only the disks by id and UUID, but also by hardware path.

Next add a line to your fstab similar to:
/dev/disk/by-path/pci-0000:03:00.0-scsi-1:0:0:0-part1 /backups auto noauto,user,noexec,rw,async 0 0


The entry will always mount the disk connected to the specified scsi port to backups. Note the -part1 for partition number.

Best,
WT

Wanna bet ?
It wasn't necessary (in this case) for you to write your own udev rules - different thing altogether.

by-path is handy in situations, but by being so specific (bus, port ...) can be a PITA also. Another option for you might be to label all your backup filesystems the same name (say BACKUP). Single line in fstab for that LABEL - then when you plug any of those disks in, they mount as above.
Won't work if you ever try to plug two in at once of course ...

Thanks for sharing wjtaylor; that tree /dev/disk is a neat technique