Wednesday, December 9, 2009

FreeBSD > Init to reboot or shutdown system

FreeBSD > Init to reboot or shutdown system
by nixcraft · 0 comments

FreeBSD init works different ways. In BSD style, it specifies the kernel security level as follows:
-1: Permanently insecure mode.
0: Insecure mode
1: Secure mode
2: Highly secure mode
3: Network secure mode

You can get current security level (FreeBSD runlevel) using sysctl command:
# sysctl –a | grep kern.securelevel

You can setup new security level in /etc/rc.conf file:
1) Open file in text editor
# vi /etc/rc.conf

2) Add or modify following:
kern_securelevel_enable="YES" # kernel security level
kern_securelevel="2" # range: -1..3 as above

3) Save the changes. Exit and restart FreeBSD.

If init used from command line i.e as a user process, init will emulate AT&T System V UNIX behavior as follows:

0: Halt and turn the power off
1: Go to single-user mode
6: Reboot the machine
c: Block further logins
q: Rescan the /etc/ttys file

1) To halt and turn the power off type:
# init 0

2) You can also use normal halt or shutdown command to shutdown system.

On most systems users can check the current runlevel with either of the following commands:

# runlevel
# who -r

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