journalctl: Add support for showing messages from a previous boot

[elogind.git] / man / journalctl.xml

diff --git a/man/journalctl.xml b/man/journalctl.xml
index b8b29b4cb5da2e6f74c9dd5193e3fbc61b356a0f..0e779b952c0813538ce47af48320eccd5339d858 100644 (file)
--- a/man/journalctl.xml
+++ b/man/journalctl.xml
@@ -327,23 +327,51 @@
                         </varlistentry>
 
                         <varlistentry>
-                                <term><option>-b</option></term>
-                                <term><option>--this-boot</option></term>
-
-                                <listitem><para>Show data only from
-                                current boot. This will add a match
-                                for <literal>_BOOT_ID=</literal> for
-                                the current boot ID of the
-                                kernel.</para></listitem>
+                                <term><option>-b <optional><replaceable>ID</replaceable></optional></option></term>
+                                <term><option>--boot=<optional><replaceable>ID</replaceable></optional></option></term>
+
+                                <listitem><para>Show messages from the specified
+                                boot <replaceable>ID</replaceable> or from
+                                current boot if no <replaceable>ID</replaceable>
+                                is given. This will add a match for
+                                <literal>_BOOT_ID=</literal>.</para>
+
+                                <para>The argument is a 128 bit ID given in
+                                short or UUID form and optionally followed by
+                                <literal>:n</literal> which identifies the nth
+                                boot relative to the boot ID given to the left
+                                of <literal>:</literal>. Supplying a negative
+                                value for n will look for a past boot and a
+                                positive value for a future boot. The boot IDs
+                                are searched for in chronological order. If no
+                                number is provided after <literal>:</literal>,
+                                <literal>-1</literal> is assumed. A value of 0
+                                is valid and equivalent to omitting
+                                <literal>:0</literal>.</para>
+
+                                <para>Alternatively, the argument may constist
+                                only of <literal>:n</literal>. In this case, a
+                                positive value will look up the nth boot
+                                starting from the beginning of the jouranl, a
+                                negative value will look up a previous boot
+                                relative to the current boot. <literal>:0</literal>
+                                will look for the current boot ID. Thus,
+                                <literal>:1</literal> is the first boot found in
+                                the journal, <literal>:2</literal> the second
+                                and so on; while <literal>:-1</literal> is the
+                                previous boot, <literal>:-2</literal> the boot
+                                before that and so on. Omitting a value after
+                                <literal>:</literal> will look for the previous
+                                boot.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>
                                 <term><option>-k</option></term>
                                 <term><option>--dmesg</option></term>
 
-                                <listitem><para>Show kernel messages from
-                                current boot. This implies <option>-b</option>
-                                and adds the match <literal>_TRANSPORT=kernel</literal>.
+                                <listitem><para>Show only kernel messages. This
+                                implies <option>-b</option> and adds the match
+                                <literal>_TRANSPORT=kernel</literal>.
                                 </para></listitem>
                         </varlistentry>
 
@@ -721,6 +749,10 @@
 
                 <programlisting>journalctl /dev/sda</programlisting>
 
+                <para>Show all kernel logs from last boot:</para>
+
+                <programlisting>journalctl -k -b :</programlisting>
+
         </refsect1>
 
         <refsect1>