Hi, I have a device with an image running core20, where I’m unable to update pi-kernel due to missing signatures: cannot perform the following tasks:\n- Fetch and check assertions for snap "pi-kernel" (927) (cannot verify snap "pi-kernel", no matching signatures found).
It’s a rare issue but I’ve encountered this before (this was a while ago so might not be 100% accurate):
- With our own snaps, where I eventually created and released a new revision.
- On a development device where I have shell access, where I removed the snap from the cache, so that it would be re-downloaded including the signature. I believe that was core20, but I’m not sure.
This also occurs on non-development devices where I don’t have shell access, so I’m not sure how to recover. Given that this is pi-kernel, I also don’t want to just try things and risk bricking them.
My questions are:
- Why/how does this happen?
- How can we avoid this?
- What can I do to resolve this?
Some extra context:
- pi-kernel is a gated snap (though I think it also happened with non-gated snaps).
- I can use the snapd REST API remotely (and run shell commands, though only from the context of another snap so I don’t think that’s helpful). I didn’t find anything relevant in the API though.
- I saw this but it doesn’t seem to apply to me (e.g. don’t have full shell access).
- Full output of
refreshvia snapd API:
{'type': 'sync', 'status-code': 200, 'status': 'OK', 'result': {'id': '7602', 'kind': 'refresh-snap', 'summary': 'Refresh "pi-kernel" snap', 'status': 'Error', 'tasks': [{'id': '25866', 'kind': 'prerequisites', 'summary': 'Ensure prerequisites for"pi-kernel" are available', 'status': 'Done', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.309417691Z', 'ready-time': '2025-06-16T06:29:27.030618672Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25867','kind': 'download-snap', 'summary': 'Download snap "pi-kernel" (927) from channel "20/stable"', 'status': 'Undone', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.309563353Z', 'ready-time':'2025-06-16T06:29:26.625555204Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25868', 'kind': 'validate-snap', 'summary': 'Fetch and check assertions for snap "pi-kernel" (927)', 'status': 'Error', 'log': ['2025-06-16T06:29:26Z ERROR cannot verifysnap "pi-kernel", no matching signatures found'], 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.309605463Z', 'ready-time': '2025-06-16T06:29:26.072734145Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25869','kind': 'mount-snap', 'summary': 'Mount snap "pi-kernel" (927)', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.309618389Z', 'ready-time': '2025-06-16T06:29:26.072582797Z', 'data': {'affected-snaps':['pi-kernel']}}, {'id': '25870', 'kind': 'run-hook', 'summary': 'Run pre-refresh hook of "pi-kernel" snap if present', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.309634611Z', 'ready-time':'2025-06-16T06:29:26.072588964Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25871', 'kind': 'stop-snap-services', 'summary': 'Stop snap "pi-kernel" services', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time':'2025-06-16T06:29:22.309659518Z', 'ready-time': '2025-06-16T06:29:26.072594963Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25872', 'kind': 'remove-aliases', 'summary': 'Remove aliases for snap "pi-kernel"', 'status': 'Hold', 'progress':{'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.309670647Z', 'ready-time': '2025-06-16T06:29:26.072601111Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25873', 'kind': 'unlink-current-snap', 'summary': 'Make currentrevision for snap "pi-kernel" unavailable', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.309679832Z', 'ready-time': '2025-06-16T06:29:26.072610148Z', 'data': {'affected-snaps': ['pi-kernel']}},{'id': '25874', 'kind': 'update-gadget-assets', 'summary': 'Update assets from kernel "pi-kernel" (927)', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.310592698Z', 'ready-time':'2025-06-16T06:29:26.072620611Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25875', 'kind': 'copy-snap-data', 'summary': 'Copy snap "pi-kernel" data', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time':'2025-06-16T06:29:22.310604382Z', 'ready-time': '2025-06-16T06:29:26.072626463Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25876', 'kind': 'setup-profiles', 'summary': 'Setup snap "pi-kernel" (927) security profiles', 'status': 'Hold','progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.310610197Z', 'ready-time': '2025-06-16T06:29:26.072632222Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25877', 'kind': 'link-snap', 'summary': 'Make snap"pi-kernel" (927) available to the system', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.310615086Z', 'ready-time': '2025-06-16T06:29:26.072637888Z', 'data': {'affected-snaps': ['pi-kernel']}},{'id': '25878', 'kind': 'auto-connect', 'summary': 'Automatically connect eligible plugs and slots of snap "pi-kernel"', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.310628956Z', 'ready-time':'2025-06-16T06:29:26.07264437Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25879', 'kind': 'set-auto-aliases', 'summary': 'Set automatic aliases for snap "pi-kernel"', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1},'spawn-time': '2025-06-16T06:29:22.310634197Z', 'ready-time': '2025-06-16T06:29:26.072657295Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25880', 'kind': 'setup-aliases', 'summary': 'Setup snap "pi-kernel" aliases', 'status': 'Hold', 'progress':{'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.310641641Z', 'ready-time': '2025-06-16T06:29:26.072663184Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25881', 'kind': 'run-hook', 'summary': 'Run post-refresh hook of"pi-kernel" snap if present', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.310653789Z', 'ready-time': '2025-06-16T06:29:26.072668962Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25882','kind': 'start-snap-services', 'summary': 'Start snap "pi-kernel" (927) services', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.310677251Z', 'ready-time': '2025-06-16T06:29:26.072674702Z', 'data':{'affected-snaps': ['pi-kernel']}}, {'id': '25883', 'kind': 'cleanup', 'summary': 'Clean up "pi-kernel" (927) install', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.310960985Z', 'ready-time':'2025-06-16T06:29:26.072681072Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25884', 'kind': 'run-hook', 'summary': 'Run configure hook of "pi-kernel" snap if present', 'status': 'Hold', 'progress': {'label': '', 'done': 1, 'total': 1},'spawn-time': '2025-06-16T06:29:22.310986076Z', 'ready-time': '2025-06-16T06:29:26.07268698Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25885', 'kind': 'run-hook', 'summary': 'Run health check of "pi-kernel" snap', 'status': 'Hold', 'progress':{'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.311018502Z', 'ready-time': '2025-06-16T06:29:26.072692109Z', 'data': {'affected-snaps': ['pi-kernel']}}, {'id': '25886', 'kind': 'check-rerefresh', 'summary': 'Monitoring snap"pi-kernel" to determine whether extra refresh steps are required', 'status': 'Done', 'progress': {'label': '', 'done': 1, 'total': 1}, 'spawn-time': '2025-06-16T06:29:22.312023939Z', 'ready-time': '2025-06-16T06:29:27.648547209Z'}], 'ready': True, 'err':'cannot perform the following tasks:\n- Fetch and check assertions for snap "pi-kernel" (927) (cannot verify snap "pi-kernel", no matching signatures found)', 'spawn-time': '2025-06-16T06:29:22.312057864Z', 'ready-time': '2025-06-16T06:29:27.648570079Z','data': {'snap-names': ['pi-kernel']}}}