NAME¶

blogd - boot logging on /dev/console

SYNOPSIS¶

/sbin/blogd [-f]

DESCRIPTION¶

The blogd daemon determines the real underlying character device of /dev/console. blogd spawns a pty/tty pair to reconnect the current /dev/console with the slave of the pty/tty pair. During writing information from this slave to the real character device a ring buffer is used to hold the information for writing it to an existing logging file.

To fetch the real tty of /dev/console the program showconsole(8) can be used. This has the advantage that blogd will not hold the real character device of /dev/console as its controlling tty (would hangup any running getty on that character device).

OPTIONS¶

-f

This option is used at shutdown, that is reboot, halt, and poweroff but also for kexec.

BOOT PARAMETERS¶

The blogd evaluates the following kernel command line parameters:

blog.silent[=1|on|yes|true]

If set, all output to the underlying character devices is suppressed. This is useful to prevent the console from being flooded with messages.

blog.coldboot[=1|on|yes|true]

If set, explicitly enables the early coldstart scan for systemd password requests (e.g. for LUKS decryption) during the initrd phase.

blog.timeout=<integer>

On s390x (64-bit IBM System/390) and z/Architecture this specifies the timeout for the MORE prompt on the 3215 console. If set to 0 the boot process does not need manual support.

SIGNALS¶

blogd knows a few signals to control its behavior.

SIGQUIT, SIGINT, and SIGTERM

will cause blogd to try to write out the ring buffer and to exit.

SIGIO

tells blogd that now it is able to write on /var/log/boot.log which means that the file system is mounted read/write and the kernel messages are written to that file. After a reboot the file /var/log/boot.old may exist where the former messages can be found including the messages at shutdown upto the point where the file systems become unmounted.

SIGSYS

tells blogd that it should stop writing to disk but continue to repeat messages to the old devices of the system console.

BUGS¶

blogd needs a mounted /proc and /dev/pts file system and tries to set the controlling tty to stdin if the real character device of /dev/console is not given. After reading /proc blogd tries to restore the status of the controlling tty to avoid problems with getty processes. This can fail because blogd forks to run in the background as a daemon.

FILES¶

/proc/<pid of blogd>/stat

the stat file of the blogd process.

/dev/console

the system console.

/var/log/boot.log, /var/log/boot.old

logging file which is created by blogd(8)

SEE ALSO¶

showconsole(8), syslogd(8), proc(5).

COPYRIGHT¶

2000,2015 Werner Fink, 2000 SuSE GmbH Nuernberg, Germany, 2015 SuSE Linux GmbH, 2026 SUSE Software Solutions Germany GmbH.

AUTHOR¶

Werner Fink <werner@suse.de>