====== Ubuntu - Grub - Grub not using UUID for the root device instead it uses /dev/sda1 or other device name ======

===== How does Grub determine the root device name? =====

By default, grub will WANT or TRY to use the UUID as the root device, UNLESS in **/etc/default/grub** you enable the feature of **GRUB_DISABLE_LINUX_UUID=true**.

  * Usually this is not there at all or it is just commented out.


Grub uses scripts in is **/etc/grub.d** which are called when you run update grub.

  * The one we really care about is the **10_linux** file.

<WRAP info>
**NOTE:**  It does not matter if your fstab is updated to use UUID, this script does not care about fstab or the current root filesystem.

  * What it does is look for entries in **/dev/disk/by-uuid** and if it finds a UUID for the root device it will assign it like normal.
    * Example:  root=UUID=theUUIDhere

</WRAP>

<WRAP info>
**NOTE:**  **/dev/disk/by-uuid** is really just a series of UUIDs in that directory that are symlinked to their actual device name.

  * This is how the grub 10_linux script associates the UUID to the root device and sets up the root=UUID. 

  * However, if it does not find a UUID entry in /dev/disk/by-uuid then it falls back to using the actual raw device name whether it be /dev/md2 or /dev/sda1 or /dev/vda1 etc...

</WRAP>

<WRAP warning>
**NOTE:**  Do not modify grub.cfg manually, as the next kernel update will cause grub to revert back to the device name.
</WRAP>