Public bug reported:
## Upgraded systems are left with a broken dpkg (flash-kernel → piboot-
try migration)
**Package:** piboot-try 1.1ubuntu0.1 / flash-kernel 3.110ubuntu2.1
**Title:** `flash-kernel → piboot-try migration does not happen on upgrade,
leaving dpkg permanently broken on Raspberry Pi`
Related: LP #2142169 (same package, different failure mode — in that
report piboot-try is installed and running; here it was never installed
at all)
### System information
Ubuntu Server 26.04 (resolute), arm64
Board: Raspberry Pi 4 Model B Rev 1.1
compatible: raspberrypi,4-model-b brcm,bcm2711
Kernel: 7.0.0-1015-raspi
piboot-try: 1.1ubuntu0.1
flash-kernel: 3.110ubuntu2.1 (was installed, now removed)
linux-firmware-raspi: 14-0ubuntu1
initramfs-tools: 0.151ubuntu1
Boot layout: A/B tryboot (/boot/firmware/{current,new}, os_prefix,
tryboot_a_b=1)
System history: installed from a 2020 image, upgraded through every release
since (kernel traces from 5.11 onwards)
### Description
On a Raspberry Pi system upgraded through successive Ubuntu releases
(originally installed from a
2020 image), `flash-kernel` was never replaced by `piboot-try`. Since
flash-kernel 3.110 dropped
Raspberry Pi support, the still-installed `flash-kernel` no longer has any
database entry matching
the board, and its initramfs hook fails on every kernel update:
```
update-initramfs: Generating /boot/initrd.img-7.0.0-1015-raspi
Unsupported platform 'Raspberry Pi 4 Model B Rev 1.1'.
run-parts: /etc/initramfs/post-update.d//flash-kernel exited with return code 1
dpkg: error processing package initramfs-tools (--configure):
old initramfs-tools package postinst maintainer script subprocess failed with
exit status 1
```
This leaves `initramfs-tools` in state `iF` and `flash-kernel` in state `it`,
which **blocks every
subsequent apt operation** — the system can no longer be updated at all,
including for security
updates.
Critically, this happens **silently**: kernel packages keep installing on `/`,
but nothing is ever
deployed to `/boot/firmware`. The machine had been running kernel 6.14.0-1017
since 2025-11-29
while 7.0.0-1014 and 7.0.0-1015 sat installed but undeployed;
`/boot/firmware/new/` had been
frozen since 2026-05-18.
### Why the migration does not happen
`linux-image-*-raspi` declares:
```
Breaks: flash-kernel
Recommends: flash-kernel | piboot-try
```
Since `flash-kernel` is already installed, the `Recommends` alternative is
satisfied and apt never
pulls `piboot-try`. The `Breaks` relationship alone does not trigger the
replacement in a normal
`apt upgrade`.
Additionally, flash-kernel 3.110ubuntu2.1 still ships obsolete conffiles from
the Pi era it no
longer supports — `/etc/flash-kernel/piboot-validate` (which documents a
`piboot-try-validate`
service that does not exist in that package) and
`/etc/flash-kernel/bootscript/bootscr.rpi` —
which makes the situation very confusing to diagnose.
### Steps to reproduce
1. Take a Raspberry Pi running an older Ubuntu release with `flash-kernel`
installed.
2. Upgrade through releases up to 26.04.
3. Run `sudo apt upgrade` when a kernel update is pending.
### Expected
The upgrade replaces `flash-kernel` with `piboot-try` automatically, or fails
loudly and early
with an actionable message.
### Actual
`dpkg` breaks, apt becomes unusable, and no kernel is deployed to the boot
partition — silently,
for months.
### Workaround
```
sudo apt install piboot-try # removes flash-kernel, unblocks dpkg
sudo apt install linux-firmware-raspi # required, otherwise boot firmware is
not copied to new/
```
Note that `linux-firmware-raspi` was not installed either on this system;
without it the deploy
step prints `find: '/usr/lib/linux-firmware-raspi': No such file or directory`
and `new/` is left
without `start4.elf` / `fixup4.dat` / `bootcode.bin`.
### Suggested fix
Make the transition automatic, e.g. by having `piboot-try`
`Replaces`/`Conflicts` in a way apt acts
on during upgrades, by having the kernel package `Depends` on `piboot-try` on
Raspberry Pi, or by
shipping a transitional `flash-kernel` on arm64 that depends on `piboot-try`
(`flash-kernel-piboot` exists but nothing pulls it in).
** Affects: flash-kernel (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "apport.piboot-try.44rhinpp.apport"
https://bugs.launchpad.net/bugs/2162655/+attachment/5988629/+files/apport.piboot-try.44rhinpp.apport
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https://bugs.launchpad.net/bugs/2162655
Title:
Upgraded systems are left with a broken dpkg (flash-kernel → piboot-
try migration)
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