fix: copy sudo binary before setting setuid bit#9
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megheaiulian merged 1 commit intomainfrom Feb 10, 2026
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symlinkJoin creates ./bin/sudo as a symlink into the Nix store. tar (without --dereference) archives symlinks as-is, so the fakeroot-tracked setuid bit on the target is silently lost. Replace the symlink with a real copy of the binary so that fakeroot can record mode 4755 on a regular file and tar faithfully preserves it in the Docker layer.
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Summary
/bin/sudo must be owned by uid 0 and have the setuid bit setwhen using the Nix image in Coder.symlinkJoincreates./bin/sudoas a symlink into the Nix store.tar(without--dereference) archives symlinks as-is, so thefakeroot-tracked setuid bit on the target is silently lost. This addscp --remove-destinationbeforechmod 4755to replace the symlink with a real file copy that tar can faithfully archive with the setuid bit preserved.Root Cause
buildLayeredImageWithNixDbusessymlinkJoininternally, which creates./bin/sudoas a symlink pointing to/nix/store/...-sudo-.../bin/sudo. ThefakeRootCommandsblock runs underfakeroot, and the resulting tar is created with--hard-dereferencebut not--dereference. Since--hard-dereferenceonly affects hard links (not symlinks), the symlink is archived as-is and symlinks in tar don't carry permission bits — the setuid bit set bychmod 4755is lost.Fix
Replace the symlink with a real copy of the binary before setting the setuid bit:
cp --remove-destination "$(readlink -f ./bin/sudo)" ./bin/sudo chmod 4755 ./bin/sudo