initrd-setup-root: Clean up whiteout entries for files to be recreated #79
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krnowak
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Nov 30, 2023
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Tested with flatcar/mantle#488 |
The removal of files in the overlay present in the lowerdir creates whiteout entries that mask the lowerdir entries. For those files that have a tmpfile rule for creation, a reboot would cause the file to be created in the upperdir, meaning this file is not updated from the lowerdir when it changes. In addition we have filtered out some tmpfile rules that caused upcopies (symlinks and directories) which meant that removing the /etc/resolv.conf symlink didn't bring it back after reboot. To make files from the lowerdir show up if they have a tmpfile rule that normally would recreate them we keep a list of whiteout entries that we clean up on boot. This also prevents freezing files because systemd-tmpfiles does not need to recreate them in the upperdir.
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The removal of files in the overlay present in the lowerdir creates whiteout entries that mask the lowerdir entries. For those files that have a tmpfile rule for creation, a reboot would cause the file to be created in the upperdir, meaning this file is not updated from the lowerdir when it changes. In addition we have filtered out some tmpfile rules that caused upcopies (symlinks and directories) which meant that removing the /etc/resolv.conf symlink didn't bring it back after reboot. To make files from the lowerdir show up if they have a tmpfile rule that normally would recreate them we keep a list of whiteout entries that we clean up on boot. This also prevents freezing files because systemd-tmpfiles does not need to recreate them in the upperdir.
How to use
Backport to Stable
Testing done
Removal of
/etc/resolv.confand reboot brings it back.Note that not all files have a tmpfiles rule, e.g.,
sshd_confighas not. We could identify files like that which need to exist for a working system by runningrm -rf /etc/*and rebooting.This is different from the removal of
/etccontents afterumount /etcwhich works without a problem and brings all files back.changelog/directory (user-facing change, bug fix, security fix, update)/bootand/usrsize, packages, list files for any missing binaries, kernel modules, config files, kernel modules, etc.