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#1 2025-05-12 21:16:02

tonimark
Member
Registered: 2021-04-05
Posts: 40

[SOLVED] mount: /new_root: wrong fs type, bad superblock on /dev/sda2

I have an old laptop:
During the boot process, I get this error:

mount: /new_root: wrong fs type, bad superblock on /dev/sda2, missing codepage or helper program, or other error
dmesg(1) may have more information after failed mount system call.
ERROR: Failed to mount 'UUID=dddec9ce-9535-46fb-a502-a03029b49e92' on real root
You are now being dropped into an emergency shell.

I know for a fact the the filesystem works fine and has no issues
by manually mounting the /dev/sda2 in /new_root at emergency shell and exiting(Ctrl+D) , the system will boot as if nothing had happened

Backstory: the laptop used to have an ext4 filesystem with both root and home partitions separated and followed the wiki https://wiki.archlinux.org/title/Btrfs# … conversion on converting the partition from ext4 to btrfs by booting from a USB stick and on the next boot, I got the error, The boot process only failed but I could still chroot into my whole installation. Then I tried several things:
1. Regenerate the initramfs both manually and by reinstalling Linux from pacman
2. Regenerate the fstab
3. Reinstalling the bootloader.
And I still get this error on boot
Btrfs check shows no issues with the filesystem, and I can still boot my system and access the files by manually mounting the /dev/sda2 to /new_root on every boot

this is the contents of fstab file 

# /dev/sda2
UUID=dddec9ce-9535-46fb-a502-a03029b49e92	/         	btrfs     	rw,relatime,ssd,discard=async,space_cache,subvol=/	0 0

# /dev/sda3
UUID=8624f555-44d9-4123-a876-3817ff88384a	/home     	btrfs     	rw,relatime,ssd,discard=async,space_cache,subvol=/	0 0

# /dev/sda1
UUID=C828-AC69      	/mnt/boot 	vfat      	rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-ro	0 2

# /mnt/dev/sda4
UUID=cd67a4ed-ed68-435b-b800-8f72559a05a7	none      	swap      	defaults  	0 0

Last edited by tonimark (2025-05-14 23:24:10)

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#2 2025-05-12 23:55:34

dakota
Member
Registered: 2016-05-20
Posts: 376

Re: [SOLVED] mount: /new_root: wrong fs type, bad superblock on /dev/sda2

Is that a typo? Because !=

UUID=dddec9e-9535-46fb-a502-a03029b49e92
UUID=dddec9ce-9535-46fb-a502-a03029b49e92

Cheers,

"Before Enlightenment chop wood, carry water. After Enlightenment chop wood, carry water." -- Zen proverb

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#3 2025-05-13 15:17:05

tonimark
Member
Registered: 2021-04-05
Posts: 40

Re: [SOLVED] mount: /new_root: wrong fs type, bad superblock on /dev/sda2

dakota wrote:

Is that a typo? Because !=

UUID=dddec9e-9535-46fb-a502-a03029b49e92
UUID=dddec9ce-9535-46fb-a502-a03029b49e92

Cheers,

Yes, I copied the error message by hand and should be the same as the fstab file

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#4 2025-05-13 18:07:12

GerBra
Forum Fellow
From: Bingen/Germany
Registered: 2007-05-10
Posts: 216

Re: [SOLVED] mount: /new_root: wrong fs type, bad superblock on /dev/sda2

Is this a UEFI Boot system and/or a GPT partion table on sda?

If so, wouldn't this need a ESP partition for booting?
# /dev/sda1
UUID=C828-AC69          /mnt/boot

Maybe i'm on the wrong way but should this sda1 go to /boot (and holding kernel+initramfs)?
I'm not very familar with UEFI + BTRFS, my systems boot from BIOS/mdos tables.

If i understand btrfs wikipage correctly the only way for an UEFI boot without a extra ESP is when using a partitionless system
https://wiki.archlinux.org/title/Btrfs# … Btrfs_disk
Don't know if this is your setup...

(Excuse my english <g>)

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#5 2025-05-13 19:59:50

seth
Member
Registered: 2012-09-03
Posts: 63,982

Re: [SOLVED] mount: /new_root: wrong fs type, bad superblock on /dev/sda2

is the device simply late?
"rootdelay=10" or "rootwait", https://wiki.archlinux.org/title/Kernel_parameters (though the latter is probably not helpful since the device seems there, just not ready?)

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#6 2025-05-14 13:03:07

tonimark
Member
Registered: 2021-04-05
Posts: 40

Re: [SOLVED] mount: /new_root: wrong fs type, bad superblock on /dev/sda2

GerBra wrote:

Is this a UEFI Boot system and/or a GPT partion table on sda?

If so, wouldn't this need a ESP partition for booting?
# /dev/sda1
UUID=C828-AC69          /mnt/boot

Maybe i'm on the wrong way but should this sda1 go to /boot (and holding kernel+initramfs)?
I'm not very familar with UEFI + BTRFS, my systems boot from BIOS/mdos tables.

If i understand btrfs wikipage correctly the only way for an UEFI boot without a extra ESP is when using a partitionless system
https://wiki.archlinux.org/title/Btrfs# … Btrfs_disk
Don't know if this is your setup...

(Excuse my english <g>)

yes this is an UEFI system and has a dedicated EFI partition but i didn't modified , i also had regenerated the intiramfs file according to wiki
the disk is partitioned in different partitions including a swap and an efi as shows from fdisk

Disk /dev/sda: 238,47 GiB, 256060514304 bytes, 500118192 sectors
Disk model: SAMSUNG MZNLN256
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: FC9C4834-A7E5-421A-98E1-8B395725A757

Device         Start       End   Sectors   Size Type
/dev/sda1      10240   1001471    991232   484M EFI System
/dev/sda2   17788928 119216127 101427200  48,4G Linux filesystem
/dev/sda3  119216128 500117503 380901376 181,6G Linux filesystem
/dev/sda4    1001472  17788927  16787456     8G Linux swap

/dev/sda2 is the root partiion while sda3 is the /home partition both were converted to BTRFS from ext4

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#7 2025-05-14 13:07:12

tonimark
Member
Registered: 2021-04-05
Posts: 40

Re: [SOLVED] mount: /new_root: wrong fs type, bad superblock on /dev/sda2

seth wrote:

is the device simply late?
"rootdelay=10" or "rootwait", https://wiki.archlinux.org/title/Kernel_parameters (though the latter is probably not helpful since the device seems there, just not ready?)

don't understand those parameters i attempted to search in /boot/grub/grub.cfg if those parameters were applied but these were returned

# cat /boot/grub/grub.cfg | grep root
set root='hd0,gpt2'
  search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 --hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2  dddec9ce-9535-46fb-a502-a03029b49e92
  search --no-floppy --fs-uuid --set=root dddec9ce-9535-46fb-a502-a03029b49e92
	set root='hd0,gpt2'
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 --hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2  dddec9ce-9535-46fb-a502-a03029b49e92
	  search --no-floppy --fs-uuid --set=root dddec9ce-9535-46fb-a502-a03029b49e92
	linux	/boot/vmlinuz-linux root=UUID=dddec9ce-9535-46fb-a502-a03029b49e92 rw rootfstype=ext4 loglevel=3 quiet
		set root='hd0,gpt2'
		  search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 --hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2  dddec9ce-9535-46fb-a502-a03029b49e92
		  search --no-floppy --fs-uuid --set=root dddec9ce-9535-46fb-a502-a03029b49e92
		linux	/boot/vmlinuz-linux root=UUID=dddec9ce-9535-46fb-a502-a03029b49e92 rw rootfstype=ext4 loglevel=3 quiet
		set root='hd0,gpt2'
		  search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 --hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2  dddec9ce-9535-46fb-a502-a03029b49e92
		  search --no-floppy --fs-uuid --set=root dddec9ce-9535-46fb-a502-a03029b49e92
		linux	/boot/vmlinuz-linux root=UUID=dddec9ce-9535-46fb-a502-a03029b49e92 rw rootfstype=ext4 loglevel=3 quiet

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#8 2025-05-14 15:04:59

seth
Member
Registered: 2012-09-03
Posts: 63,982

Re: [SOLVED] mount: /new_root: wrong fs type, bad superblock on /dev/sda2

https://raw.githubusercontent.com/torva … meters.txt
You're supposed to *add* them to see whether just waiting a bit before attempting to mount the device helps.

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#9 2025-05-14 23:23:30

tonimark
Member
Registered: 2021-04-05
Posts: 40

Re: [SOLVED] mount: /new_root: wrong fs type, bad superblock on /dev/sda2

seth wrote:

https://raw.githubusercontent.com/torva … meters.txt
You're supposed to *add* them to see whether just waiting a bit before attempting to mount the device helps.

seth wrote:

is the device simply late?
"rootdelay=10" or "rootwait", https://wiki.archlinux.org/title/Kernel_parameters (though the latter is probably not helpful since the device seems there, just not ready?)

perhaps there was a misunderstanding I thought you were asking to see if these parameters were present and not to add them
Maybe if you had added "try to add  those parameters to your kernel on boot" after the question mark I would have understood better
I tried adding "rootdelay=10" as you told as boot parameter but nothing has changed.... oh wait, there was a leftover setting from previous installation
turns out at

GRUB_CMDLINE_LINUX=

the 

rootfstype=

was ext4 instead of btrfs, as it should,by changing it to btrfs and regenerating the grub config fixed the issue

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#10 2025-05-14 23:27:12

tonimark
Member
Registered: 2021-04-05
Posts: 40

Re: [SOLVED] mount: /new_root: wrong fs type, bad superblock on /dev/sda2

don't forget to update the https://wiki.archlinux.org/title/Btrfs# … conversion to reflect that grub config file needs to be modfied

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#11 2025-05-14 23:50:56

Scimmia
Fellow
Registered: 2012-09-01
Posts: 12,693

Re: [SOLVED] mount: /new_root: wrong fs type, bad superblock on /dev/sda2

Why would you be using rootfstype in the first place? There shouldn't be anything to update because that shouldn't need to be specified either way.

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