Commit 3c8b8db0 authored by Eli Zaretskii's avatar Eli Zaretskii
Browse files

Document backup-by-copying-when-privileged-mismatch.

parent 34d90e29
......@@ -606,7 +606,10 @@ locally (@pxref{File Variables}).
@vindex backup-by-copying
@vindex backup-by-copying-when-linked
@vindex backup-by-copying-when-mismatch
The choice of renaming or copying is controlled by three variables.
@vindex backup-by-copying-when-privileged-mismatch
@cindex file ownership, and backup
@cindex backup, and user's uid
The choice of renaming or copying is controlled by four variables.
Renaming is the default choice. If the variable
@code{backup-by-copying} is non-@code{nil}, copying is used. Otherwise,
if the variable @code{backup-by-copying-when-linked} is non-@code{nil},
......@@ -615,7 +618,12 @@ may still be used when the file being edited has only one name. If the
variable @code{backup-by-copying-when-mismatch} is non-@code{nil}, then
copying is used if renaming would cause the file's owner or group to
change. @code{backup-by-copying-when-mismatch} is @code{t} by default
if you start Emacs as the superuser.
if you start Emacs as the superuser. The fourth variable,
@code{backup-by-copying-when-privileged-mismatch}, gives the highest
numeric user id for which @code{backup-by-copying-when-mismatch} will be
forced on. This is useful when low-numbered uid's are assigned to
special system users, such as @code{root}, @code{bin}, @code{daemon},
etc., which must maintain ownership of files.
When a file is managed with a version control system (@pxref{Version
Control}), Emacs does not normally make backups in the usual way for
......
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