[sysvinit.git] / doc / bootlogd.README


bootlogd: a way to capture all console output during bootup
          in a logfile.

- bootlogd opens /dev/console and finds out what the real console is
  with an ioctl() if TIOCCONS is available
- otherwise bootlogd tries to parse /proc/cmdline for console=
  kernel command line arguments
- then opens the (most probable) real console
- allocates a pty pair
- redirects console I/O to the pty pair
- then goes in a loop reading from the pty, writing to the real
  console and a logfile as soon as a r/w partition is available,
  buffering in memory until then.

As soon as bootlogd exits or gets killed, the pty is closed and the
redirection will be automatically undone by the kernel. So that's
pretty safe.
Commit	Line	Data
	1
	2	bootlogd: a way to capture all console output during bootup
	3	in a logfile.
	4
	5	- bootlogd opens /dev/console and finds out what the real console is
	6	with an ioctl() if TIOCCONS is available
	7	- otherwise bootlogd tries to parse /proc/cmdline for console=
	8	kernel command line arguments
	9	- then opens the (most probable) real console
	10	- allocates a pty pair
	11	- redirects console I/O to the pty pair
	12	- then goes in a loop reading from the pty, writing to the real
	13	console and a logfile as soon as a r/w partition is available,
	14	buffering in memory until then.
	15
	16	As soon as bootlogd exits or gets killed, the pty is closed and the
	17	redirection will be automatically undone by the kernel. So that's
	18	pretty safe.
	19