- a-z, 0-9. All strings should be in UTF-8 format, and
- non-printable characters should not be used. If double
- or single quotes or backslashes are to be used within
- variable assignments they should be escaped with
- backslashes, following shell style. It is not
- supported to concatenate multiple individually quoted
- strings. Lines beginning with "#" shall be ignored as
- comments.</para>
-
- <para><filename>/etc/os-release</filename> contains
- data that is defined by the operating system vendor
- and should not be changed by the administrator.</para>
+ a-z, 0-9. Shell special characters ("$", quotes,
+ backslash, backtick) must be escaped with backslashes,
+ following shell style. All strings should be in UTF-8
+ format, and non-printable characters should not be used.
+ It is not supported to concatenate multiple individually
+ quoted strings. Lines beginning with "#" shall be
+ ignored as comments.</para>
+
+ <para>The file <filename>/etc/os-release</filename>
+ takes precedence over
+ <filename>/usr/lib/os-release</filename>. Applications
+ should check for the former, and exclusively use its
+ data if it exists, and only fall back to
+ <filename>/usr/lib/os-release</filename> if it is
+ missing. Applications should not read data from both
+ files at the same
+ time. <filename>/usr/lib/os-release</filename> is the
+ recommended place to store OS release information as
+ part of vendor trees.
+ <filename>/etc/os-release</filename> should be a
+ relative symlink to
+ <filename>/usr/lib/os-release</filename>,
+ to provide compatibility with applications only
+ looking at <filename>/etc</filename>. A relative
+ symlink instead of an absolute symlink is
+ necessary to avoid breaking the link in a chroot or
+ initrd environment such as dracut.</para>
+
+ <para><filename>os-release</filename> contains data
+ that is defined by the operating system vendor and
+ should generally not be changed by the
+ administrator.</para>