Public bug reported:
After updating the kernel, the final regeneration of grub.cfg ended
without any boot-entries.
I use zfs and normally they are generated fine by
/etc/grub.d/10_linux_zfs
The only hint for reasons, why the script might have failed, can be
found in /var/log/apt/term.log. All lines are normal, except for the
"date" one:
...
Found linux image: vmlinuz-6.8.0-111-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found initrd image: initrd.img-6.8.0-111-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found linux image: vmlinuz-6.8.0-110-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found initrd image: initrd.img-6.8.0-110-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found linux image: vmlinuz-6.8.0-107-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found initrd image: initrd.img-6.8.0-107-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found linux image: vmlinuz-6.8.0-85-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found initrd image: initrd.img-6.8.0-85-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found linux image: vmlinuz-6.8.0-83-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found initrd image: initrd.img-6.8.0-83-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
date: ungültiges Datum »@“
^^^^^^^^^^^^^^^^^^^^^^^^^^
Warning: os-prober will be executed to detect other bootable partitions.
Its output will be used to detect bootable binaries on them and create new boot
entries.
Adding boot menu entry for UEFI Firmware Settings ...
The german message means "invalid date". I assume this message comes
from line 668 in 10_linux_zfs:
666 # Snapshot date
667 foo="$(get_field_from_entry "${entry}" 5)"
668 snapdate="$(date -d @$(get_field_from_entry "${entry}" 5) "+%x @
%H:%M")"
and that column 5 in ${entry} for some reason does not contain the unix
timestamp, that is normally found there. Since I can not reproduce this,
I do not know, what this unexpected value was. But snapshots are created
and removed quite often, so it could be pure coincidence, that a
snapshot might have been caught in an intermediate state.
Maybe it is possible to harden the script, that it would skip such a
broken entry instead of resulting in no bootable grub.cfg entry at all.
Note, that I am using Linux Mint and I can report there instead. But my
impression is, that this is an upstream (=Ubuntu) bug or annoyance and
fixing it would help Ubuntu users as well.
# lsb_release -rd
No LSB modules are available.
Description: Linux Mint 22.3
Release: 22.3
# apt-cache policy grub-common
grub-common:
Installiert: 2.12-1ubuntu7.3
Installationskandidat: 2.12-1ubuntu7.3
Versionstabelle:
*** 2.12-1ubuntu7.3 500
500 http://ftp.hosteurope.de/mirror/archive.ubuntu.com
noble-updates/main amd64 Packages
100 /var/lib/dpkg/status
2.12-1ubuntu7 500
500 http://ftp.hosteurope.de/mirror/archive.ubuntu.com noble/main amd64
Packages
Expected to happen (at the end of kernel update): a new grub.cfg file
gets generated, which contains entries for all installed bootable
kernels.
happened instead: the new grub.cfg only contains entry for UEFI firmware
settings, bot no boot entry for any of the installed kernels. This
happened only at the moment of the post-installation script. A later
call to grub-mkconfig produced a correct grub.cfg.
** Affects: grub2 (Ubuntu)
Importance: Undecided
Status: New
** Description changed:
After updating the kernel, the final regeneration of grub.cfg ended
without any boot-entries.
I use zfs and normally they are generated fine by
/etc/grub.d/10_linux_zfs
The only hint for reasons, why the script might have failed, can be
found in /var/log/apt/term.log. All lines are normal, except for the
"date" one:
...
Found linux image: vmlinuz-6.8.0-111-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found initrd image: initrd.img-6.8.0-111-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found linux image: vmlinuz-6.8.0-110-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found initrd image: initrd.img-6.8.0-110-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found linux image: vmlinuz-6.8.0-107-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found initrd image: initrd.img-6.8.0-107-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found linux image: vmlinuz-6.8.0-85-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found initrd image: initrd.img-6.8.0-85-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found linux image: vmlinuz-6.8.0-83-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Found initrd image: initrd.img-6.8.0-83-generic in
rpool/ROOT/ubuntu_idiiu4@zfs-auto-snap_daily-2026-05-14-1040
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
Warning: didn't find any valid initrd or kernel.
date: ungültiges Datum »@“
^^^^^^^^^^^^^^^^^^^^^^^^^^
Warning: os-prober will be executed to detect other bootable partitions.
Its output will be used to detect bootable binaries on them and create new
boot entries.
Adding boot menu entry for UEFI Firmware Settings ...
The german message means "invalid date". I assume this message comes
from line 668 in 10_linux_zfs:
- 666 # Snapshot date
- 667 foo="$(get_field_from_entry "${entry}" 5)"
- 668 snapdate="$(date -d @$(get_field_from_entry "${entry}" 5) "+%x @
%H:%M")"
+ 666 # Snapshot date
+ 667 foo="$(get_field_from_entry "${entry}" 5)"
+ 668 snapdate="$(date -d @$(get_field_from_entry "${entry}" 5) "+%x @
%H:%M")"
and that column 5 in ${entry} for some reason does not contain the unix
timestamp, that is normally found there. Since I can not reproduce this,
- I do not know, what this unexpected value was. Bit snapshots are created
+ I do not know, what this unexpected value was. But snapshots are created
and removed quite often, so it could be pure coincidence, that a
snapshot might have been caught in an intermediate state.
Maybe it is possible to harden the script, that it would skip such a
- broken entry instead of resulting in not bootable grub.cfg entry at all.
+ broken entry instead of resulting in no bootable grub.cfg entry at all.
Note, that I am using Linux Mint and I can report there instead. But my
- impression is, that this is an upstream (=Ubuntu) bug or annoyance.
+ impression is, that this is an upstream (=Ubuntu) bug or annoyance and
+ fixing it would help Ubuntu users as well.
# lsb_release -rd
No LSB modules are available.
Description: Linux Mint 22.3
Release: 22.3
# apt-cache policy grub-common
grub-common:
- Installiert: 2.12-1ubuntu7.3
- Installationskandidat: 2.12-1ubuntu7.3
- Versionstabelle:
- *** 2.12-1ubuntu7.3 500
- 500 http://ftp.hosteurope.de/mirror/archive.ubuntu.com
noble-updates/main amd64 Packages
- 100 /var/lib/dpkg/status
- 2.12-1ubuntu7 500
- 500 http://ftp.hosteurope.de/mirror/archive.ubuntu.com noble/main
amd64 Packages
+ Installiert: 2.12-1ubuntu7.3
+ Installationskandidat: 2.12-1ubuntu7.3
+ Versionstabelle:
+ *** 2.12-1ubuntu7.3 500
+ 500 http://ftp.hosteurope.de/mirror/archive.ubuntu.com
noble-updates/main amd64 Packages
+ 100 /var/lib/dpkg/status
+ 2.12-1ubuntu7 500
+ 500 http://ftp.hosteurope.de/mirror/archive.ubuntu.com noble/main
amd64 Packages
Expected to happen (at the end of kernel update): a new grub.cfg file
gets generated, which contains entries for all installed bootable
kernels.
happened instead: the new grub.cfg only contains entry for UEFI firmware
settings, bot no boot entry for any of the installed kernels. This
happened only at the moment of the post-installation script. A later
call to grub-mkconfig produced a correct grub.cfg.
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https://bugs.launchpad.net/bugs/2153118
Title:
grub2 10_linux_zfs fails with "invalid date: @"
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