Getting A Grub Menu Via The Serial Port
Add either of the two lines to /boot/grub/grub.conf in order to make
grub's interface available on the serial port. Obviously change the
parameters to match your equipment, these values are rather default.
# for serial and console
serial --unit=0 --speed=9600 --word=8 --parity=no --stop=1 terminal --timeout=10 serial console
# just serial
serial --unit=0 --speed=9600 --word=8 --parity=no --stop=1 terminal serial
Serial Console
Just for reference if you want a console on the serial port after
grub (for times sshd isn't working).
Disclaimer: I have been using these notes without revision for many years,
they have worked from 7.3 to RHEL4-U3 but it is quite possible
some steps are no longer necessary or considered the "best" solution.
- add
console=tty0 console=ttyS0,9600n81
to the end of your kernel line in /boot/grub/grub.conf.
- add
ST:12345:respawn:/sbin/mgetty /dev/ttyS0 -s 9600 -r
to /etc/inittab
- add the following 5 lines to /etc/mgetty+sendfax/mgetty.config
# serial console
port ttyS0
direct y
speed 9600
toggle-dtr n
You might have to modify /etc/securetty (ie add "ttyS0") to permit root logins.
Depending on circumstances you may want to also enable the magic sysreq key in /etc/sysctl.conf to permit remote reboots (among other things) when the system is too locked up for a regular /sbin/reboot. Read the documentation before doing this, there is a reason it is called "magic."