Playing with Grub
=================
Some context, on my laptop, I have 2 SSD (nvme) and 3 OS installed (Windows, Linux Mint and Ubuntu). I wanted the following behavior:
- Linux Mint and Ubuntu have their own grub
- Linux Mint and Ubuntu don't share the same SWAP partition(s).
- Boot first in the Linux Mint Grub Menu
- Linux Mint Grub Menu:
- Being able to open the Ubuntu Grub Menu
- Not being able to run Ubuntu directly
- Being able to run Windows
- Ubuntu Grub Menu:
- Being able to open the Linux Mint Grub Menu
- Not being able to run Linux Mint directly
- Being able to run Windows
Get Partitions UUID
###################
When manipulating grub and boot parameters, we often need to get the UUID of the partitions, you can get it with the command:
.. code-block:: bash
sudo blkid
For example in my case I have the following partitions:
.. code-block:: text
/dev/nvme0n1p3: UUID="291bd5e4-dbc4-4b54-aa7b-6329d43f35ce" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="0c3719af-0ad2-4b1a-8f44-12a3ba07734b"
/dev/nvme0n1p1: UUID="5B0D-4E6B" BLOCK_SIZE="512" TYPE="vfat" PARTLABEL="EFI System Partition" PARTUUID="e4067cfd-bfb1-42a0-bfe4-629526f151f8"
/dev/nvme0n1p4: UUID="a1fdc046-256f-486b-a26e-0972460c812b" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="7ef875d9-95fc-478d-b772-971033799107"
/dev/nvme0n1p2: UUID="234744c8-ed3b-4f2b-a9c1-55dbc71c87ac" TYPE="swap" PARTUUID="132b0b66-7217-480f-a5af-f59713e43306"
/dev/nvme1n1p4: BLOCK_SIZE="512" UUID="1602C35902C33C8D" TYPE="ntfs" PARTUUID="b91115c2-c01e-458b-a713-2498b4e15eae"
/dev/nvme1n1p9: UUID="4585ba2e-a70a-4455-ab59-2eff7742d169" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="ae391fcd-8545-49ab-88b5-c720f6f4d5b6"
/dev/nvme1n1p12: UUID="9f0cf58b-0b2a-49d9-9995-ae7a301317db" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="c60653be-38ed-4af4-885d-bd85e6c90a82"
/dev/nvme1n1p7: LABEL="DELLSUPPORT" BLOCK_SIZE="512" UUID="104E7D674E7D468E" TYPE="ntfs" PARTUUID="66bd551f-2482-4121-8c66-0830fe0f179a"
/dev/nvme1n1p10: UUID="1ebbde4d-c3f2-47b2-a4ac-76f85c60ee38" TYPE="swap" PARTUUID="4c575959-bc0c-4219-ab3c-65194dbca3cc"
/dev/nvme1n1p5: LABEL="WINRETOOLS" BLOCK_SIZE="512" UUID="D8A2972DA2970F5E" TYPE="ntfs" PARTUUID="aa834c21-8c15-44d2-8a8c-5d9dfbbeb508"
/dev/nvme1n1p3: TYPE="BitLocker" PARTLABEL="Basic data partition" PARTUUID="d0f71a8b-6ef3-4524-82af-e939b8e16d47"
/dev/nvme1n1p1: UUID="9C57-4B3F" BLOCK_SIZE="512" TYPE="vfat" PARTLABEL="EFI system partition" PARTUUID="53cfb120-4349-487b-bbe0-e38871ac10d0"
/dev/nvme1n1p8: UUID="6EF8-B15E" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="f28ad5d2-5cbd-4908-9492-5d6e0f56f59b"
/dev/nvme1n1p11: UUID="0351dc8e-4a77-4f40-bf22-cbf1c0d9c043" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="7d1d4d89-45c3-42bd-9050-990a71180263"
/dev/nvme1n1p6: LABEL="Image" BLOCK_SIZE="512" UUID="98FC9779FC97507C" TYPE="ntfs" PARTUUID="f486223d-4e9d-4e52-a313-90aff77b99e8"
/dev/loop1: TYPE="squashfs"
/dev/loop2: TYPE="squashfs"
/dev/loop0: TYPE="squashfs"
/dev/nvme1n1p2: PARTLABEL="Microsoft reserved partition" PARTUUID="dd2a760e-1b6b-4d8b-a756-bad6f240af7f"
/dev/loop3: TYPE="squashfs"
.. warning::
Careful not to mix between UUID and partUUID (most of the time you just need the UUID)
Get Mount points
################
Using the **lsblk** give a human readable view of the mount points of the currently running distribution:
Output from Linux Mint:
.. code-block:: text
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
loop0 7:0 0 63,2M 1 loop /snap/core20/1634
loop1 7:1 0 63,2M 1 loop /snap/core20/1695
loop2 7:2 0 48M 1 loop /snap/snapd/17336
loop3 7:3 0 49,6M 1 loop /snap/snapd/17576
sda 8:0 1 0B 0 disk
nvme0n1 259:0 0 931,5G 0 disk
├─nvme0n1p1 259:2 0 512M 0 part /boot/efi
├─nvme0n1p2 259:3 0 60,5G 0 part [SWAP]
├─nvme0n1p3 259:4 0 810,4G 0 part /home
└─nvme0n1p4 259:5 0 60G 0 part /
nvme1n1 259:1 0 953,9G 0 disk
├─nvme1n1p1 259:6 0 100M 0 part
├─nvme1n1p2 259:7 0 16M 0 part
├─nvme1n1p3 259:8 0 543,3G 0 part
├─nvme1n1p4 259:9 0 947M 0 part
├─nvme1n1p5 259:10 0 990M 0 part
├─nvme1n1p6 259:11 0 16,6G 0 part
├─nvme1n1p7 259:12 0 1,3G 0 part
├─nvme1n1p8 259:13 0 488M 0 part
├─nvme1n1p9 259:14 0 977M 0 part
├─nvme1n1p10 259:15 0 61G 0 part
├─nvme1n1p11 259:16 0 65,2G 0 part
└─nvme1n1p12 259:17 0 263G 0 part
Output from Ubuntu:
.. code-block:: text
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
loop0 7:0 0 4K 1 loop /snap/bare/5
loop1 7:1 0 55,6M 1 loop /snap/core18/2620
loop2 7:2 0 63,2M 1 loop /snap/core20/1623
loop3 7:3 0 63,2M 1 loop /snap/core20/1634
loop4 7:4 0 164,8M 1 loop /snap/gnome-3-28-1804/161
loop5 7:5 0 346,3M 1 loop /snap/gnome-3-38-2004/119
loop6 7:6 0 91,7M 1 loop /snap/gtk-common-themes/1535
loop7 7:7 0 45,9M 1 loop /snap/snap-store/599
loop8 7:8 0 48M 1 loop /snap/snapd/17336
loop9 7:9 0 284K 1 loop /snap/snapd-desktop-integration/14
loop10 7:10 0 169,4M 1 loop /snap/spotify/60
sda 8:0 1 0B 0 disk
nvme0n1 259:0 0 931,5G 0 disk
├─nvme0n1p1 259:1 0 512M 0 part
├─nvme0n1p2 259:2 0 60,5G 0 part
├─nvme0n1p3 259:3 0 810,4G 0 part
└─nvme0n1p4 259:4 0 60G 0 part
nvme1n1 259:5 0 953,9G 0 disk
├─nvme1n1p1 259:6 0 100M 0 part
├─nvme1n1p2 259:7 0 16M 0 part
├─nvme1n1p3 259:8 0 543,3G 0 part
├─nvme1n1p4 259:9 0 947M 0 part
├─nvme1n1p5 259:10 0 990M 0 part
├─nvme1n1p6 259:11 0 16,6G 0 part
├─nvme1n1p7 259:12 0 1,3G 0 part
├─nvme1n1p8 259:13 0 488M 0 part /boot/efi
├─nvme1n1p9 259:14 0 977M 0 part /boot
├─nvme1n1p10 259:15 0 61G 0 part [SWAP]
├─nvme1n1p11 259:16 0 65,2G 0 part /
└─nvme1n1p12 259:17 0 263G 0 part /home
Grub: ignoring a partition
##########################
If you want grub to ignore another OS, you can ask grub to ignore a specific partition (the one containing the kernels = root partition `/` ) so that it won't scan for it when grub is being updated.
You need to edit the file `/etc/default/grub` and set the parameter **GRUB_OS_PROBER_SKIP_LIST**.
Ignoring Ubuntu entries in Linux Mint Grub (`/etc/default/grub`):
.. code-block:: text
# Ignoring Ubuntu root Partition ( `/`)
GRUB_OS_PROBER_SKIP_LIST="0351dc8e-4a77-4f40-bf22-cbf1c0d9c043@/dev/nvme1n1p11"
Ignoring Linux Mint entries in Ubuntu Grub (`/etc/default/grub`):
.. code-block:: text
# Ignoring Linux mint root Partition ( `/`)
GRUB_OS_PROBER_SKIP_LIST="a1fdc046-256f-486b-a26e-0972460c812b@/dev/nvme0n1p4"
Grub: Link to another grub
##########################
Adding the Ubuntu Grub in the Linux Mint grub (to be added in `/etc/grub.d/40_custom`):
.. code-block:: text
menuentry 'Ubuntu Grub' {
insmod chain
search --no-floppy --fs-uuid --set=root 4585ba2e-a70a-4455-ab59-2eff7742d169
configfile /grub/grub.cfg
}
Adding the Linux Mint Grub in the Ubuntu grub (to be added in `/etc/grub.d/40_custom`):
.. code-block:: text
menuentry 'Mint Grub' {
insmod chain
search --no-floppy --fs-uuid --set=root a1fdc046-256f-486b-a26e-0972460c812b
configfile /boot/grub/grub.cfg
}
.. warning::
You need to set the UUID of the partition containing the /boot/grub/grub.cfg file of the **OTHER** grub.
If the other grub has a `/boot` partition then you need to write the UUID of the /boot partition and write the path of the config file **WITHOUT** the `/boot` prefix.
If the other grub does not have a `/boot` partition then you need to write the UUID of the root partition `/` and write the path of the config file **WITH** the `/boot` prefix.
You can get the partition of the /boot/grub/grub.cfg file using the command:
.. code-block:: bash
# From Linux Mint
df -T /boot/grub/grub.cfg
# Filesystem Type 1K-blocks Used Available Use% Mounted on
# /dev/nvme0n1p4 ext4 61646628 38707212 19775464 67% /
# From Ubuntu
df -T /boot/grub/grub.cfg
# Filesystem Type 1K-blocks Used Available Use% Mounted on
# /dev/nvme1n1p9 ext4 965872 179908 719560 21% /boot
Managing boot entries from Linux
################################
You can manipulate (view/add/remove/change) boot entries with the command line tool: `efibootmgb` (Add `-v` for verbose info)
To view the current state of your boot, just run the command without any argument:
.. code-block:: bash
efibootmgb
Output:
.. code-block:: text
BootCurrent: 0000
Timeout: 0 seconds
BootOrder: 0000,0002,0004,0003,0001,0005
Boot0000* Mint
Boot0001* UEFI PM981a NVMe Samsung 1024GB S4GXNX0NB09373 1
Boot0002* Ubuntu
Boot0003* UEFI Samsung SSD 970 EVO Plus 1TB S4EWNZ0R200729F 1
Boot0004* Windows Boot Manager
Boot0005* UEFI PM981a NVMe Samsung 1024GB S4GXNX0NB09373 1 2
Example to add Ubuntu and Mint boot entries. You need to identify the EFI partition (/boot/efi) that the OS uses, in my case:
- nvme0n1p1 for Linux Mint
- nvme1n1p8 for Ubuntu
.. code-block:: bash
sudo efibootmgr -c -d /dev/nvme1n1 -p 8 -L Ubuntu -l "\EFI\ubuntu\shimx64.efi"
sudo efibootmgr -c -d /dev/nvme0n1 -p 1 -L Mint -l "\EFI\ubuntu\shimx64.efi"
Examle to update the boot order:
.. code-block:: bash
sudo efibootmgr -o 0000,0002,0004,0003,0001,0005
------------------------------------------------------------
**Sources**: