sysupdate: Support volatile-root for finding the root partition #25242
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poettering
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Nov 10, 2022
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looks conceptually OK. but please rework to just stat() the path stored in that file, to derive major/minor, see comments. |
I guess that is obsolete: just use stat(), and then the codepaths will look totally different anyway. |
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The existing logic can't find the root device in scenarios where the root has been replaced with an overlay. We support looking at "/run/systemd/volatile-root" to find the original root, similar to what systemd-repart and gpt-auto-generator do.
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The existing logic can't find the root device in scenarios where the root has been replaced with an overlay. This adds logic to look at
/run/systemd/volatile-rootto find the original root. This is similar to whatsystemd-repartandgpt-auto-generatoralready do (references: #20612, #20578).I tested this change by using
mkosito build an Ubuntu 22.04 image booted withsystemd.volatile=overlay. Without this change,systemd-sysupdatecan't find the root device; with this change, it gets through the logic to find the root device and proceeds to query the transfer source.Fixes #25241
NOTE: My biggest question is whether it makes sense to minimally duplicate this logic as the PR presently does vs. extract out the
volatile-root-checking logic in a utility function. I opted to go with the former as the logic in sysupdate intentionally looks at/usrand not/(unlikesystemd-repart, which does) and it seemed prudent to preserve that behavior.