Re: disks, partitions, slices, etc.

[Ramiro Aceves <ea1abz%gmail.com@localhost>]

El 5/10/26 a las 18:59, Jeff escribió:
> Just to follow up with results:
>
> I did create the ext2 filesystem with "newfs_ext2fs", then I mounted it in NetBSD and created some test files.  I rebooted into Gentoo and tried to mount it, but got an error about a block overlap, 
> saying that the filesystem needed to be repaired.
>
> I logged back into NetBSD and ran fsck_ext2fs on it, which did not report anything. Then rebooted into Gentoo and still got the error. So I ran fsck on it in Gentoo. It moved a ton of blocks, 
> periodically warning of the potential for data loss. When it was done, I was able to mount the partition in Gentoo. The text file that I had created in the top level of the partition in NetBSD was 
> still there, but the directory containing two other test files was gone. I recreated them in Gentoo, then rebooted into NetBSD. The partition still mounted fine there, and all files that had been 
> visible in Gentoo were present.
>
> So, what worked for me was:
> - create ext2 filesystem in NetBSD
> - fsck it in NetBSD (possibly unnecessary)
> - fsck it in Gentoo
>
> I'll continue to test it going back and forth and see if it's stable now.
>
> Thanks again,
> Jeff

Hi Jeff,

I can confirm what you observed. I created an ext2 filesystem in NetBSD in a spare pendrive, copied 5 GB of files and when I tried to mount it in Debian it failed:

netbsd-nuc# fdisk /dev/sd1
fdisk: Cannot determine the number of heads
Disk: /dev/sd1
NetBSD disklabel disk geometry:
cylinders: 65535, heads: 16, sectors/track: 63 (1008 sectors/cylinder)
total sectors: 120164352, bytes/sector: 512

BIOS disk geometry:
cylinders: 1023, heads: 255, sectors/track: 63 (16065 sectors/cylinder)
total sectors: 120164352

Partitions aligned to 2048 sector boundaries, offset 63

Partition table:
0: Linux native (sysid 131)
    start 63, size 120164289 (58674 MB, Cyls 0-7479/225/42)
        PBR is not bootable: All bytes are identical (0x00)
1: <UNUSED>
2: <UNUSED>
3: <UNUSED>
Bootselector disabled.
No active partition.
Drive serial number: 0 (0x00000000)
netbsd-nuc#



netbsd-nuc# disklabel sd1
# /dev/rsd1:
type: SCSI
disk:  SanDisk 3.2Gen1
label: fictitious
flags: removable
bytes/sector: 512
sectors/track: 63
tracks/cylinder: 16
sectors/cylinder: 1008
cylinders: 65535
total sectors: 120164352
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0		# microseconds
track-to-track seek: 0	# microseconds
drivedata: 0

5 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 d: 120164352         0     unused      0     0        # (Cyl.      0 - 119210*)
 e: 120164289        63 Linux Ext2      0     0        # (Cyl.      0*- 119210*)
disklabel: boot block size 0
disklabel: super block size 0
netbsd-nuc#

netbsd-nuc# newfs_ext2fs /dev/rsd1e
/dev/rsd1e: 58673.9MB (120164289 sectors) block size 4096, fragment size 4096
	using 459 block groups of 128.0MB, 32768 blks, 16384 inodes.
super-block backups (for fsck_ext2fs -b #) at:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,


root@debian-nuc8i7:~# mount -t ext2 /dev/sdb1 /root/disco_ext4/
mount: /root/disco_ext4: fsconfig() failed: Structure needs cleaning.
       dmesg(1) may have more information after failed mount system call.


root@debian-nuc8i7:~# fsck -y /dev/sdb1
fsck from util-linux 2.41.5
e2fsck 1.47.2 (1-Jan-2025)
ext2fs_check_desc: Corrupt group descriptor: bad block for block bitmap
fsck.ext2: Group descriptors look bad... trying backup blocks...
Block bitmap for group 1 is not in group.  (block 0)
Relocate? yes

Inode bitmap for group 1 is not in group.  (block 0)
Relocate? yes

Inode table for group 1 is not in group.  (block 0)
WARNING: SEVERE DATA LOSS POSSIBLE.
Relocate? yes

Block bitmap for group 2 is not in group.  (block 33793)
Relocate? yes

Inode bitmap for group 2 is not in group.  (block 33794)
Relocate? yes

Inode table for group 2 is not in group.  (block 33795)
WARNING: SEVERE DATA LOSS POSSIBLE.
Relocate? yes

Block bitmap for group 3 is not in group.  (block 0)
Relocate? yes

Inode bitmap for group 3 is not in group.  (block 0)
Relocate? yes

Inode table for group 3 is not in group.  (block 0)
WARNING: SEVERE DATA LOSS POSSIBLE.
Relocate? yes

Block bitmap for group 4 is not in group.  (block 65536)
Relocate? yes

Inode bitmap for group 4 is not in group.  (block 65537)
Relocate? yes

Inode table for group 4 is not in group.  (block 65538)
WARNING: SEVERE DATA LOSS POSSIBLE.
Relocate? yes

Block bitmap for group 5 is not in group.  (block 0)
Relocate? yes

Inode bitmap for group 5 is not in group.  (block 0)
Relocate? yes

Inode table for group 5 is not in group.  (block 0)

..
..

I stopped it.

Regards.
Ramiro.