The most basic operation a download manager needs to perform is to download a file from a URL. Here’s how you would use wget to download a file:

 1) Login as root user

2) Open /etc/inittab file using vi text editor or gedit GUI text editor

# vi /etc/inittab

3) Replace runlevel 3 to 5:
From:

id:3:initdefault:

To:

id:5:initdefault:

4) Save the changes.

[root@]# more /etc/inittab

#

# inittab       This file describes how the INIT process should set up

#               the system in a certain run-level.

#

# Author:       Miquel van Smoorenburg,

#               Modified for RHS Linux by Marc Ewing and Donnie Barnes

#

# 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:3:initdefault:

# System initialization.

si::sysinit:/etc/rc.d/rc.sysinit

l0:0:wait:/etc/rc.d/rc 0

l1:1:wait:/etc/rc.d/rc 1

l2:2:wait:/etc/rc.d/rc 2

l3:3:wait:/etc/rc.d/rc 3

l4:4:wait:/etc/rc.d/rc 4

l5:5:wait:/etc/rc.d/rc 5

l6:6:wait:/etc/rc.d/rc 6

# Trap CTRL-ALT-DELETE

ca::ctrlaltdel:/sbin/shutdown -t3 -r now

# When our UPS tells us power has failed, assume we have a few minutes

# of power left.  Schedule a shutdown for 2 minutes from now.

# This does, of course, assume you have powerd installed and your

# UPS connected and working correctly.  

pf::powerfail:/sbin/shutdown -f -h +2 "Power Failure; System Shutting Down"

# If power was restored before the shutdown kicked in, cancel it.

pr:12345:powerokwait:/sbin/shutdown -c "Power Restored; Shutdown Cancelled"

# Run gettys in standard runlevels

1:2345:respawn:/sbin/mingetty tty1

2:2345:respawn:/sbin/mingetty tty2

3:2345:respawn:/sbin/mingetty tty3

4:2345:respawn:/sbin/mingetty tty4

5:2345:respawn:/sbin/mingetty tty5

6:2345:respawn:/sbin/mingetty tty6

# Run xdm in runlevel 5

x:5:respawn:/etc/X11/prefdm -nodaemon

 cat /proc/cpuinfo

to get centOS unix version

cat /etc/redhat-release 

 Usage: /usr/bin/groups [OPTION]... [USERNAME]...

[root@]# groups apache

by ggarron

 There are some situations when you need to start a second X session on your computer.

If you are running KDE the solution is quite simple, just go to

K->Leave->Switch User

and if you are not using KDE, the solution is still easy :),

Hit ALT+CTRL+F2

and log in the new terminal window, now run inside it.

More read:http://www.go2linux.org/start%20second%20X%20session%20xinit%20startx

 type in: 

#last

or

#cd /var/log 

#cat secure* | grep Accepted > login.txt 

The * is to read from the backup logs also omit if you don't want to see those 

this will show all successful logins 

you can also use sshd in place of Accepted to show all attempts and Accepted 

then 
#pico login.txt 
or nano or your other favorite text editor to read

 Check the RHEL repos, but useful cmds include:

 1. Redhat Linux release is now know as Redhat Enterprise Linux and is fully supported by Redhat and its release started with version 1. Whereas 
Fedora is a Redhat unsupported release.
2) Redhat Enterprise Linux is a tested version and are extracted from fedora. Whereas fedora is a testing bed where all are allowed to put their codes, knowledge, etc to develop, which if good is put in fedora.
3) Redhat costs you, whereas Fedora is free.
4) There is certification on RHEL Whereas on fedora there is no certification

 lspci is a great utility for listing the system hardware. (Anything on the PCI bus, anyway.)

cat /proc/cpuinfo - Displays CPU info

cat /proc/meminfo - Displays memory info

dmesg (or cat /var/log/dmesg) contains some info, not necessarily everything.

If you have a RedHat/CentOS system, you can use sosreport to collect a good bit of information, though I don't know if it has all the hardware info listed in it.