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The device map file /boot/grub/device.map is in this format:

(disk) /dev/device

So, for example, on a system with a floppy and a single SCSI disk, the file would look like this:

(fd0) /dev/fd0
(hd0) /dev/sda

I try to display its content : 

cat /boot/grub/device.map

I get this error: No such file or directory

Is it renamed or it is a new hierarchy of Linux system?

muru
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Abdennour TOUMI
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1 Answers1

23

The device map is not installed by default with grub2. You can create a device map by typing the following into your console:

sudo grub-mkdevicemap

This will put device.map into the /boot/grub directory.

Fuzzy Analysis
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    how does linux determine the hdX to sdX mapping before grub-mkdevicemap is run ? – sherpaurgen Feb 07 '19 at 06:37
  • linux uses whatever the grub boot location is in the grub.cfg 'root' property (or similar). http://140.120.7.21/LinuxRef/BootingLinux/Grub2.html – Fuzzy Analysis Feb 20 '19 at 02:59
  • @satch_boogie Linux does not rely on the Grub device map, as clearly shown [in the Grub manual](https://www.gnu.org/software/grub/manual/grub/html_node/Device-map.html). It's the other way around. Grub tries to guess the mapping that Linux chooses by itself. In fact, Linux works fine even [without Grub installed](https://en.wikipedia.org/wiki/SYSLINUX). – jpaugh Apr 12 '20 at 23:18
  • When I run grub-customize, it gives me an error if there's not device.map. Your solution is wonderful. And to generate grub.cfg, it's grub-mkconfig. – Quidam Apr 27 '20 at 15:02
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    But I have the error that says that it's not possible to get the canonical path for /cow when trying grub-mkconfig. – Quidam Apr 27 '20 at 15:06