Missing initrd.img-core in os.snap

Metadata

Project: snapcraft (launchpad)
Number: #1740882
Type: issue
State: closed
Author: ~p-pisati
Labels: —
Created: 2018-01-02 03:21 PM UTC
Updated: 2021-08-25 09:58 PM UTC
Closed: 2018-02-09 03:59 PM UTC

Current evaluation

Kernel plugin looked for initrd.img-core at the obsolete /usr/lib path after base snaps moved it to /boot. Fixed by merged PR #1839 (commit aaf5e68b1) updating the path to boot/initrd.img.

Resolution: closed resolved

Reason: Launchpad bug #1740882 was fixed by snapcraft PR #1839, merged as commit aaf5e68b1 "kernel plugin: update initrd.img-core path to boot/initrd.img", which changed _unpack_generic_initrd() to read boot/initrd.img from the os.snap instead of /usr/lib/ubuntu-core-generic-initrd/initrd.img-core. Follow-up commit a4e4d3e90 (#1867) removed the fragile python-magic dependency that produced the TypeError, and the bug was closed as resolved.

Evaluated by: mr-cal-bot

No scores available.

Issue body

I'm puzzled by this new "behaviour" of the kernel plugin in snapcraft - it's reproducible in every version i tried (2.35...2.38). $ cat snapcraft.yaml name: kernel version: 4.13.16+ summary: Linux kernel description: The upstream Linux kernel grade: stable confinement: strict type: kernel parts: kernel: plugin: kernel source: . source-type: git kernel-with-firmware: false $ cd linux-vanilla (any recent vanilla linux tree will work, i'm using stable/linux-4.13.y FWIW) $ make defconfig $ snapcraft ... Generating driver initrd for kernel release: 4.13.16+ Parallel unsquashfs: Using 4 processors 2 inodes (2 blocks) to write [===========================================================================================================================================|] 2/2 100% created 0 files created 4 directories created 2 symlinks created 0 devices created 0 fifos ... Traceback (most recent call last): [3252/9137] File "/home/flag/canonical/snapcraft/bin/snapcraft", line 36, in <module> obj=dict(project=snapcraft.ProjectOptions())) File "/usr/lib/python3/dist-packages/click/core.py", line 716, in __call__ return self.main(*args, **kwargs) File "/usr/lib/python3/dist-packages/click/core.py", line 696, in main rv = self.invoke(ctx) File "/usr/lib/python3/dist-packages/click/core.py", line 1037, in invoke return Command.invoke(self, ctx) File "/usr/lib/python3/dist-packages/click/core.py", line 889, in invoke return ctx.invoke(self.callback, **ctx.params) File "/usr/lib/python3/dist-packages/click/core.py", line 534, in invoke return callback(*args, **kwargs) File "/usr/lib/python3/dist-packages/click/decorators.py", line 17, in new_func return f(get_current_context(), *args, **kwargs) File "/home/flag/canonical/snapcraft/snapcraft/cli/__init__.py", line 124, in run ctx.forward(lifecyclecli.commands['snap']) File "/usr/lib/python3/dist-packages/click/core.py", line 552, in forward return self.invoke(cmd, **kwargs) File "/usr/lib/python3/dist-packages/click/core.py", line 534, in invoke return callback(*args, **kwargs) File "/home/flag/canonical/snapcraft/snapcraft/cli/lifecycle.py", line 140, in snap project_options, directory=directory, output=output) File "/home/flag/canonical/snapcraft/snapcraft/internal/lifecycle/_packer.py", line 45, in snap execute('prime', project_options) File "/home/flag/canonical/snapcraft/snapcraft/internal/lifecycle/_runner.py", line 80, in execute _Executor(config, project_options).run(step, part_names) File "/home/flag/canonical/snapcraft/snapcraft/internal/lifecycle/_runner.py", line 175, in run self._run_step(step, part, part_names) File "/home/flag/canonical/snapcraft/snapcraft/internal/lifecycle/_runner.py", line 212, in _run_step getattr(part, step)() File "/home/flag/canonical/snapcraft/snapcraft/internal/pluginhandler/__init__.py", line 330, in build self.plugin.build() File "/home/flag/canonical/snapcraft/snapcraft/plugins/kbuild.py", line 258, in build self.do_install() File "/home/flag/canonical/snapcraft/snapcraft/plugins/kernel.py", line 473, in do_install self._make_initrd() File "/home/flag/canonical/snapcraft/snapcraft/plugins/kernel.py", line 286, in _make_initrd initrd_unpacked_path = self._unpack_generic_initrd() File "/home/flag/canonical/snapcraft/snapcraft/plugins/kernel.py", line 255, in _unpack_generic_initrd mime_type = mime_detector.file(os.path.realpath(tmp_initrd_path)) File "/home/flag/.local/lib/python3.5/site-packages/magic.py", line 134, in file return str(r, 'utf-8') TypeError: coercing to str: need a bytes-like object, NoneType found so i added the following debug patch and snapped again: diff --git a/snapcraft/plugins/kernel.py b/snapcraft/plugins/kernel.py index c1e81e4..e388c2c 100644 --- a/snapcraft/plugins/kernel.py +++ b/snapcraft/plugins/kernel.py @@ -60,6 +60,7 @@ import glob import logging import magic import os +import pty import shutil import subprocess import tempfile @@ -248,6 +249,11 @@ class KernelPlugin(kbuild.KBuildPlugin): mime_detector.load() # Make sure we're getting the mime type of the actual initrd, not # a symbolic link. + logger.info('tmp_initrd_path: {}\n'.format(os.path.realpath(tmp_initrd_path))) + myfile = os.path.realpath(tmp_initrd_path) + if not os.path.exists(myfile): + logger.info('Missing initrd, spwaning a shell') + pty.spawn("/bin/dash") mime_type = mime_detector.file(os.path.realpath(tmp_initrd_path)) if not mime_type: raise RuntimeError( $ snapcraft ... created 0 files created 4 directories created 2 symlinks created 0 devices created 0 fifos tmp_initrd_path: /tmp/tmp27aod6nv/squashfs-root/boot/initrd.img-core Missing initrd, spwaning a shell $ find /tmp/tmp27aod6nv/squashfs-root/ /tmp/tmp27aod6nv/squashfs-root/ /tmp/tmp27aod6nv/squashfs-root/usr /tmp/tmp27aod6nv/squashfs-root/usr/lib /tmp/tmp27aod6nv/squashfs-root/usr/lib/ubuntu-core-generic-initrd /tmp/tmp27aod6nv/squashfs-root/usr/lib/ubuntu-core-generic-initrd/initrd.img-core-0.7.43+ppa23 /tmp/tmp27aod6nv/squashfs-root/usr/lib/ubuntu-core-generic-initrd/initrd.img-core $ ls -la /tmp/tmp27aod6nv/squashfs-root/usr/lib/ubuntu-core-generic-initrd total 8 drwxr-xr-x 2 flag flag 4096 nov 30 18:38 . drwxr-xr-x 3 flag flag 4096 nov 30 18:38 .. lrwxrwxrwx 1 flag flag 29 nov 30 18:37 initrd.img-core -> ../../../boot/initrd.img-core lrwxrwxrwx 1 flag flag 42 nov 30 18:37 initrd.img-core-0.7.43+ppa23 -> ../../../boot/initrd.img-core-0.7.43+ppa23 $ cat /tmp/tmp27aod6nv/squashfs-root/usr/lib/ubuntu-core-generic-initrd/initrd.img-core cat: /tmp/tmp27aod6nv/squashfs-root/usr/lib/ubuntu-core-generic-initrd/initrd.img-core: No such file or directory Manually unsquashing os.snap, there's this: $ unsquashfs -d foobar ./parts/kernel/src/os.snap $ find foobar -name \initrd\* foobar/boot/initrd.img-core-0.7.43+ppa23 foobar/boot/initrd.img-core foobar/lib/systemd/system/initrd-switch-root.service foobar/lib/systemd/system/initrd-parse-etc.service foobar/lib/systemd/system/initrd-fs.target foobar/lib/systemd/system/initrd-root-fs.target foobar/lib/systemd/system/initrd-cleanup.service foobar/lib/systemd/system/initrd-switch-root.target foobar/lib/systemd/system/initrd-udevadm-cleanup-db.service foobar/lib/systemd/system/initrd.target foobar/usr/lib/ubuntu-core-generic-initrd/initrd.img-core-0.7.43+ppa23 foobar/usr/lib/ubuntu-core-generic-initrd/initrd.img-core $ ls -la foobar/usr/lib/ubuntu-core-generic-initrd/initrd.img-core lrwxrwxrwx 1 flag flag 29 nov 30 18:37 foobar/usr/lib/ubuntu-core-generic-initrd/initrd.img-core -> ../../../boot/initrd.img-core $ md5sum foobar/usr/lib/ubuntu-core-generic-initrd/initrd.img-core e4b9d74334b4f40ec07e1ee20c48462b foobar/usr/lib/ubuntu-core-generic-initrd/initrd.img-core Was initrd.img-core moved from usr/lib/ubuntu-core-generic-initrd to boot without updating the kernel plugin?

Evaluation history

Date	Model	Scores	Action	Summary
2026-10-03 01:11 PM UTC	stealth/space-bunny-alpha	—	closed resolved	Kernel plugin looked for initrd.img-core at the obsolete /usr/lib path after base snaps moved it to /boot. Fixed by merged PR #1839 (commit aaf5e68b1) updating the path to boot/initrd.img.
2026-09-30 11:44 PM UTC	stealth/space-bunny-alpha	—	closed resolved	Kernel plugin looked for initrd.img-core at the obsolete /usr/lib path after base snaps moved it to /boot. Fixed by merged PR #1839 (commit aaf5e68b1), which now reads boot/initrd.img.
2026-09-25 08:50 AM UTC	stealth/space-bunny-alpha	—	closed resolved	Fixed by merged PR #1839: the kernel plugin now reads boot/initrd.img from os.snap instead of the obsolete initrd.img-core path (commit aaf5e68b1).
2026-09-13 05:16 PM UTC	qwen/qwen3.6-35b-a3b	—	—	Abandoned. Snapcraft's kernel plugin failed to locate initrd.img-core due to a broken symlink, causing a build crash. No fix or follow-up was provided.
2026-07-23 03:43 PM UTC	qwen/qwen3.6-35b-a3b	—	—	Closed without resolution. The snapcraft kernel plugin failure caused by a missing initrd.img-core symlink appears abandoned or superseded by newer versions.
2026-07-22 02:14 PM UTC	qwen/qwen3.6-35b-a3b	—	—	A kernel snap build failure caused by a missing initrd.img-core symlink was closed without comments or fixes, indicating abandonment. No resolution or merge details were provided.
2026-07-04 10:29 AM UTC	qwen3.6-35b-a3b-mtp-q6	—	—	Closed without resolution. The initrd.img-core symlink bug in the snapcraft kernel plugin was abandoned due to inactivity, with no fix implemented.

Update history

Date	Change
2021-08-25 09:58 PM UTC	created

Related work

Likely Fixed By: canonical/snapcraft#1839 (confidence 97%)
Merged PR referenced in the issue comments by ~ogra; commit aaf5e68b1 updates the initrd.img-core path to boot/initrd.img.
Related To: canonical/snapcraft#1867 (confidence 62%)
Commit a4e4d3e90 removed the python-magic dependency in the kernel plugin that raised the TypeError in the traceback.

Related issues

Issue	Project	State	Summary	Similarity
#1567564 kernel plugin should use initrd from /boot in the os snap, not from /usr/lib	snapcraft (launchpad)	closed	Kernel plugin initrd lookup was fixed by switching to /boot/initrd.img-core in snapcraft PR #1839, merged as commit aaf5e68b1.	80%
#1839 kernel plugin: update initrd.img-core path to boot/initrd.img	snapcraft	merged	Merged PR #1839 as commit aaf5e68b1, updating the kernel plugin to use boot/initrd.img instead of initrd.img-core and fixing LP bug #1740882.	74%
#1627923 kernel plugin initrd packaging fails when kernel modules have common dependencies	snapcraft (launchpad)	closed	Fixed by snapcore/snapcraft PR #837, which allowed initrd packaging to handle common kernel-module dependencies without duplicate-copy failures.	70%