linuxrc: Log initramfs output/commands

By default, any {bad,good,warn}_msg output and external command calls
will now be logged to /tmp/init.log in initramfs. This can be turned
off via gk.log.disabled={1,yes} kernel command-line argument.

This is especially helpful when working with remote servers when you
can access initramfs system through SSH.

In addition, initramfs' log file can be preserved, i.e. copied to
real system just before switch_root call. This can be controlled
via gk.log.keep kernel command-line argument: When just enabled,
initramfs will copy log to $NEWROOT/genkernel-boot.log. Keep in my
that the file path must be accessible for initramfs and by default,
initramfs will only mount / as $NEWROOT and no additional mountpoints.

Signed-off-by: Thomas Deutschmann <whissi@gentoo.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/doc/genkernel.8.txt b/doc/genkernel.8.txt
index f5f877d..3ab28ce 100644
--- a/doc/genkernel.8.txt
+++ b/doc/genkernel.8.txt
@@ -760,6 +760,22 @@ recognized by the kernel itself.
 *debug*::
     Drop into a debug shell early in the process.
 
+*gk.log.disabled*=<...>::
+    By default, any shown message and external command calls will be logged
+    to '/tmp/init.log' in initramfs. This boolean option allows you to
+    disable logging for some reason.
+
+*gk.log.keep*=<...>::
+When set to a boolean value, genkernel will preserve '/tmp/init.log',
+see above, and copy file to '/genkernel-boot.log' on *root* device.
+You can also set your own file like '/root/my-genkernel-boot.log' to
+copy log to a custom path.
+
+NOTE: The default file '/genkernel-boot.log' on *root* was chosen because
+genkernel's initramfs will only mount root filesystem by default. If you
+want to store the log file in '/var/log/genkernel-boot.log' for example
+make sure that this mountpoint is accessible, see *initramfs.mounts*.
+
 *noload*=<...>::
     List of modules to skip loading.
     Separate using commas or spaces.