dmesg
The main purpose of dmesg is to display kernel messages. dmesg can provide helpful
information in case of hardware problems or problems with loading a module into the kernel.
In addition, with dmesg, you can determine what hardware is installed on your server. During
every boot, Linux checks your hardware and logs information about it. You can view these
logs using the command /bin/dmesg.

ulimit
This command is built into the bash shell and is used to provide control over the resources
available to the shell and to the processes started by it on systems that allow such control.
Use the -a option to list all parameters that we can set:
ulimit -a
The -H and -S options specify the hard and soft limits that can be set for the given resource.

daemons
On Novell SUSE and Red Hat Enterprise Linux systems, the /sbin/chkconfig command
provides the administrator with an easy-to-use interface to change start options for various
daemons. One of the first commands that should be run when using chkconfig is a check for
all running daemons:
/sbin/chkconfig --list | grep on
/sbin/service sendmail stop
/etc/init.d/cups status

Changing runlevels
To set the initial runlevel of a machine at boot, modify the /etc/inittab, start Linux without starting
the GUI, set the run level to 3.
# Default runlevel. The runlevels used by RHS are:
#   0 - halt (Do NOT set initdefault to this)
#   1 - Single user mode
#   2 - Multiuser, without NFS (The same as 3, if you do not have networking)
#   3 - Full multiuser mode
#   4 - unused
#   5 - X11
#   6 - reboot (Do NOT set initdefault to this)
#
id:5:initdefault: