Q4OS Forum

Totone

Member

Registered: 2026-01-20

Posts: 64

[Resolved] setup_s4-snapshot ...

Bonjour toutes et tous,
Hello everyone,

I regularly perform backups using `setup_s4-snapshot` (every ten days); the backups appear to be valid and run without any error messages or issues.
However, for the last three backups, the following has appeared, and I don't know if it's serious or how to resolve it:

File /run/s4-snapshot/bind-root-overlay/rootu/var/lib/smartmontools/attrlog.SPCC_Solid_State_Disk-WWDD250314050004249.ata.csv changed size while reading filesystem, attempting to re-read

Unrecognised xattr prefix system.posix_acl_access
Unrecognised xattr prefix system.posix_acl_access

Unrecognised xattr prefix system.posix_acl_access
Unrecognised xattr prefix system.posix_acl_access
Unrecognised xattr prefix system.posix_acl_access

Unrecognised xattr prefix system.posix_acl_access
Unrecognised xattr prefix system.posix_acl_access
Unrecognised xattr prefix system.posix_acl_access

Unrecognised xattr prefix system.posix_acl_access
Unrecognised xattr prefix system.posix_acl_access
Unrecognised xattr prefix system.posix_acl_access
Unrecognised xattr prefix system.posix_acl_access
Unrecognised xattr prefix system.posix_acl_access

Unrecognised xattr prefix system.posix_acl_access

Unrecognised xattr prefix system.posix_acl_access

Unrecognised xattr prefix system.posix_acl_access
[=========================================================/] 813573/813573 100%

ISO image produced: 13317195 sectors
Written to medium : 13317195 sectors at LBA 0
Writing to 'stdio:/media/xxxxxx/poubsvg/q4os/snapshot/snapshot-20260720_1029.iso' completed successfully.

isohybrid: Warning: more than 1024 cylinders: 26011
isohybrid: Not all BIOSes will be able to boot this device

Regards
[Resolved]

Last edited by Totone (2026-07-23 10:47)

q4osteam

Q4OS Team

Registered: 2015-12-06

Posts: 6,317

Website

Re: [Resolved] setup_s4-snapshot ...

None of these are anything to worry about - they're all generic warnings from the underlying tools (mksquashfs and isohybrid) that S4 Snapshot uses, not signs of a problem with your backup:

  - The smartmontools log size-change warning just means that log file was actively being written to while the snapshot was being captured - expected for
  any live-system backup and doesn't affect the result.
  - "Unrecognised xattr prefix system.posix_acl_access" is a standard mksquashfs message about POSIX ACL extended attributes it doesn't specifically remap.
  It's cosmetic - this is a very common message and doesn't mean your ACLs or files are broken.
  - The isohybrid "more than 1024 cylinders... Not all BIOSes will be able to boot" warning is isohybrid's own built-in sanity check about legacy
  CHS-addressing limits from very old BIOSes. It fires on essentially any ISO of a reasonable size these days. Every modern BIOS and all UEFI firmware use
  LBA addressing and are unaffected - this only matters if you're specifically targeting genuinely ancient (1990s-era) hardware.

Your backups are valid and complete - these three lines are just noise you can ignore.