by
<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
<option>--setup-keys</option>
- command), forward secure sealing (FSS) for
- all persistent journal files is
- enabled.</para></listitem>
+ command), forward secure sealing (FSS)
+ for all persistent journal files is
+ enabled. FSS is based on <ulink
+ url="http://eprint.iacr.org/2013/397">Seekable
+ Sequential Key Generators</ulink> by
+ G. A. Marson and B. Poettering and
+ may be used to protect journal files
+ from unnoticed
+ alteration.</para></listitem>
</varlistentry>
<varlistentry>
while the former apply if persistent
logging is enabled and the system is
fully booted
- up. <varname>SystemMaxUse=</varname>
+ up. <command>journalctl</command> and
+ <command>systemd-journald</command>
+ ignore all files with names not ending
+ with <literal>.journal</literal> or
+ <literal>.journal~</literal>, so only
+ such files, located in the appropriate
+ directories, are taken into account
+ when calculating current disk usage.
+ </para>
+
+ <para><varname>SystemMaxUse=</varname>
and <varname>RuntimeMaxUse=</varname>
control how much disk space the
journal may use up at
that usually seven rotated journal
files are kept as history. Specify
values in bytes or use K, M, G, T, P,
- E as units for the specified
- sizes. Note that size limits are
- enforced synchronously to journal
- files as they are extended, and need
- no explicit rotation step triggered by
- time.</para></listitem>
+ E as units for the specified sizes
+ (equal to 1024, 1024²,... bytes).
+ Note that size limits are enforced
+ synchronously when journal files
+ are extended, and no explicit
+ rotation step triggered by
+ time is needed.</para></listitem>
</varlistentry>
<varlistentry>