fix(update): use kernel from updated root instead of boot partition #41
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When updating the bootloader configuration, the code was using filepath.Glob() to find kernels on the boot partition. This returned files in alphabetical order, which caused the wrong kernel to be selected when multiple versions existed. For example, with kernels 6.18.2-surface-1 and 6.18.3-surface-2 on the boot partition, the bootloader would point to 6.18.2 (alphabetically first) even though the updated root filesystem contained 6.18.3. This caused boot failures because the kernel modules didn't match the booted kernel. The fix adds getUpdatedRootKernelVersion() which reads the kernel version from the updated root's /usr/lib/modules directory, ensuring the bootloader always references the kernel that matches the newly extracted container image. Includes regression tests that verify: - Kernel version is detected from updated root, not boot partition - Newest kernel is selected when multiple versions exist - Various kernel version formats are handled correctly
bsherman
approved these changes
Jan 7, 2026
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Pull request overview
This PR fixes a critical bug in the update mechanism where the bootloader would select an incorrect kernel version when multiple kernels existed on the boot partition. The issue stemmed from using filepath.Glob() which returns files in alphabetical order, potentially selecting an older kernel (e.g., 6.18.2) instead of the newer one from the updated root (e.g., 6.18.3), causing boot failures due to module mismatches.
Key Changes:
- Introduced
getUpdatedRootKernelVersion()to detect kernel version from the updated root's/usr/lib/modulesdirectory - Updated both GRUB2 and systemd-boot update paths to use the new detection method
- Added comprehensive regression tests covering various kernel version formats and edge cases
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| pkg/update.go | Adds getUpdatedRootKernelVersion() function and updates updateGRUBBootloader() and updateSystemdBootBootloader() to use it instead of filepath.Glob() for kernel selection |
| pkg/update_test.go | Adds comprehensive tests for getUpdatedRootKernelVersion() including edge cases (multiple kernels, missing vmlinuz, various version formats) and regression test verifying the fix |
When updating the bootloader configuration, the code was using filepath.Glob() to find kernels on the boot partition. This returned files in alphabetical order, which caused the wrong kernel to be selected when multiple versions existed. For example, with kernels 6.18.2-surface-1 and 6.18.3-surface-2 on the boot partition, the bootloader would point to 6.18.2 (alphabetically first) even though the updated root filesystem contained 6.18.3. This caused boot failures because the kernel modules didn't match the booted kernel. The fix adds getUpdatedRootKernelVersion() which reads the kernel version from the updated root's /usr/lib/modules directory, ensuring the bootloader always references the kernel that matches the newly extracted container image. Includes regression tests that verify: - Kernel version is detected from updated root, not boot partition - Newest kernel is selected when multiple versions exist - Various kernel version formats are handled correctly
Signed-off-by: Brian Ketelsen <bketelsen@gmail.com>
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When updating the bootloader configuration, the code was using filepath.Glob() to find kernels on the boot partition. This returned files in alphabetical order, which caused the wrong kernel to be selected when multiple versions existed.
For example, with kernels 6.18.2-surface-1 and 6.18.3-surface-2 on the boot partition, the bootloader would point to 6.18.2 (alphabetically first) even though the updated root filesystem contained 6.18.3. This caused boot failures because the kernel modules didn't match the booted kernel.
The fix adds getUpdatedRootKernelVersion() which reads the kernel version from the updated root's /usr/lib/modules directory, ensuring the bootloader always references the kernel that matches the newly extracted container image.
Includes regression tests that verify: