Commits on Sep 4, 2026

1. shadow-core: commit several files together, and convert the last six … …

   …tools
   
   group and gshadow have to agree: a group present in one and absent from
   the other is a broken system, and every tool that touches a group touches
   both. Committing them one at a time leaves a window in which they
   disagree, and a failure in the second makes that permanent.
   
   commit_all validates every file before writing any, which closes the
   failure this actually hits -- a value that would corrupt a record is
   rejected while nothing has been touched, instead of after the first file
   is already on disk. A genuine I/O error partway through can still leave
   the set half applied; there is no journal, and a rollback that can itself
   fail would not be an improvement. All the locks are held until the last
   write finishes, so no other process sees the intermediate state.
   
   A commit that would write the same bytes now writes nothing. A rewrite is
   not free: it replaces the inode and moves the mtime, and for an unchanged
   empty file it failed outright, since the atomic writer refuses to produce
   a zero-length file. Every tool used to carry its own 'did anything
   change' flag to work around that; those are gone. Found by usermod's
   tests, whose fixture has an empty gshadow that -G does not touch.
   
   groupmod, useradd, usermod, userdel, pwck and grpck are converted, and
   there is no longer a single FileLock::acquire left in any tool. userdel
   loses its hand-rolled line filter, which had its own idea of which lines
   were comments next to the parser that already knows; one consequence is
   that a comment above a removed account now moves to the end of the file
   rather than staying in place, which is what every other tool already did.
   
   Exit codes are preserved, including the two pwck keeps for a failed
   write: 6 'can not sort' and 5 'can not update the files' stay distinct by
   matching on the file the error names.
   
   Verified against a prefix tree for each tool: useradd creating an account
   with a user group, supplementary groups, aging and subid; usermod
   renaming across four files and replacing a group list; groupmod moving a
   GID and following it into passwd; userdel removing an account from six
   files; grpck sorting group and gshadow together, keeping each comment
   with its group, and writing nothing on a second run.

   

   pierre-warnier committed Sep 4, 2026
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