man: document explicitly tha ReadWritePaths= cannot undo superblock read-only settings

Fixes: #29266
This commit is contained in:
Lennart Poettering 2023-11-08 15:36:43 +01:00
parent 0bc649d6b0
commit b6be6a6721

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@ -1631,7 +1631,12 @@ StateDirectory=aaa/bbb ccc</programlisting>
permit this. Nest <varname>ReadWritePaths=</varname> inside of <varname>ReadOnlyPaths=</varname> in
order to provide writable subdirectories within read-only directories. Use
<varname>ReadWritePaths=</varname> in order to allow-list specific paths for write access if
<varname>ProtectSystem=strict</varname> is used.</para>
<varname>ProtectSystem=strict</varname> is used. Note that <varname>ReadWritePaths=</varname> cannot
be used to gain write access to a file system whose superblock is mounted read-only. On Linux, for
each mount point write access is granted only if the mount point itself <emphasis>and</emphasis> the
file system superblock backing it are not marked read-only. <varname>ReadWritePaths=</varname> only
controls the former, not the latter, hence a read-only file system superblock remains
protected.</para>
<para>Paths listed in <varname>InaccessiblePaths=</varname> will be made inaccessible for processes inside
the namespace along with everything below them in the file system hierarchy. This may be more restrictive than