Question: Years ago i installed ubuntu on a hard drive in my computer. A few days ago, after the release of 18.04, i bought a ssd and reinstalled everything on that. The old hdd is still linked in the computer - just to look up things.

GRUB does index the old hdd as secondary boot option. But i will never ever boot the old system again. So is there any way to remove the old hard drive from the grub options?

Answer: 
The easiest (GUI) way is to run **grub-customizer**

```
$ sudo add-apt-repository ppa:danielrichter2007/grub-customizer
$ sudo apt-get update
$ sudo apt-get install grub-customizer

```
You can use the `GRUB_OS_PROBER_SKIP_LIST` option to selectively disable scanning devices. So for example, if you want to exclude /dev/sdb1 and /dev/sdc1, first you need to find out their `UUID`:

```
blkid | grep -E 'sdb1|sdc1'

```

Will output something like:

```
/dev/sdb1: LABEL="bkp_root" UUID="1-2-3-4-5" TYPE="ext4" PARTUUID="123"
/dev/sdc1: LABEL="bkp2_root" UUID="a-b-c-d-e" TYPE="ext4" PARTUUID="abc"

```

Then write the option to `/etc/default/grub` using this format:

```
GRUB_OS_PROBER_SKIP_LIST="1-2-3-4-5@/dev/sdb1 a-b-c-d-e@/dev/sdc1"

```

Finally, when you run `sudo update-grub` it will inform you of the changes:

```
Skipped Ubuntu 18.04.5 LTS (18.04) on /dev/sdb1 by user request.
Skipped Ubuntu 18.04.5 LTS (18.04) on /dev/sdc1 by user request.

```