voici ce que me donne la commande tune2fs (par rapport au tuto évoqués par Jtro et Manchette, merci à eux)
tune2fs -l /dev/sda2 | grep Block
tune2fs: Bad magic number in super-block while trying to open /dev/sda2
j'ai aussi lancé un btrfs scrub
voici la réponse=
btrfs scrub status /dev/sda2
UUID: 1c00bd9d-d77c-49d8-ad5f-926cb11dc4bc
Scrub started: Sun Aug 30 06:24:26 2020
Status: finished
Duration: 0:02:29
Total to scrub: 14.41GiB
Rate: 99.02MiB/s
Error summary: no errors found
et aussi (en root) un btrfs checkbtrfs check --repair /dev/sda2
enabling repair mode
WARNING:
Do not use --repair unless you are advised to do so by a developer
or an experienced user, and then only after having accepted that no
fsck can successfully repair all types of filesystem corruption. Eg.
some software or hardware bugs can fatally damage a volume.
The operation will start in 10 seconds.
Use Ctrl-C to stop it.
10 9 8 7 6 5 4 3 2 1
Starting repair.
Opening filesystem to check...
Checking filesystem on /dev/sda2
UUID: 1c00bd9d-d77c-49d8-ad5f-926cb11dc4bc
[1/7] checking root items
Fixed 0 roots.
[2/7] checking extents
No device size related problem found
[3/7] checking free space cache
cache and super generation don't match, space cache will be invalidated
[4/7] checking fs roots
[5/7] checking only csums items (without verifying data)
[6/7] checking root refs
[7/7] checking quota groups
Rescan hasn't been initialzied, a difference in qgroup accounting is expected
Counts for qgroup id: 1/0 are different
our: referenced 14718066688 referenced compressed 14718066688
disk: referenced 12310667264 referenced compressed 12310667264
diff: referenced 2407399424 referenced compressed 2407399424
our: exclusive 941031424 exclusive compressed 941031424
disk: exclusive 940146688 exclusive compressed 940146688
diff: exclusive 884736 exclusive compressed 884736
Repair qgroup 1/0
Repair qgroup status item
found 14832349184 bytes used, no error found
total csum bytes: 13847792
total tree bytes: 638697472
total fs tree bytes: 588890112
total extent tree bytes: 31817728
btree space waste bytes: 105401760
file data blocks allocated: 894620401664
referenced 31634178048
quelqu'un d'un peu calé peut il me faire un diagnostic?