SYSTEM COMMANDS

uname -a

Display linux system information

uname -r

Display kernel release information

last reboot

Show system reboot history

date

Show current date and time

cal

Show current month calendar4

whoami

Who you are logged in as

finger user

Display information about user

cat /proc/cpuinfo

Show cpu info

cat /proc/meminfo

Show memory information

man command

Show manual for command

df

Check filesytem storage

du

Check subdirectories

df -h

Shows file size which is user readable

du --max-depth=1 -h

Check subdirectories by one level down

whereis app

Show possible location of app

which app

Show which app will be run by default

free

To check ram & swap partition usuage

free -g

To see usuage in gigabytes

How to create swap file in linux?

dd if=/dev/zero of=/swapfile bs=1024 count=1024

dd to create a storage file

if=/dev/zero : Read from /dev/zero file. /dev/zero is a special file,in that provides as many null characters to build storage file called /swapfile.
of=/swapfile : Read from /dev/zero write storage file to /swapfile.
bs=1024 : Read and write 1024 BYTES bytes at a time.
count=1024 : Copy only 1024 BLOCKS input blocks.

mkswap /swapfile

To setup a linux swap area in a file.

swapon /swapfile
Enable the swap file.

swapoff /swapfile

Disable the swap file.

Determine the size of the new swap file in megabytes and multiply by 1024 to determine the number of blocks. For example, the block size of a 64 MB swap file is 65536.

lvextend -l +100 /logical/volume00

Extend the logical volume 00 from blank space i.e. 0mb to volume 00 with 100 mb...

ctrl+alt+f1

GUI (Graphical mode) to text mode i.e. CLI(Command Line Interface)

ctrl+alt+f7

Text to graphic mode

Types Of Boot Loader
grub grand unified boot loader
lilo linux bootloader

kcontrol &

Configure the kde enviroment

gnome-control-center

Configure the gnome enviroment

switchdesk kde

Set the default startup to kde

switchdesk gnome

Set the default startup to gnome

up2date-config

Configure the red hat for update

mount /dev/sda1 /tmpdir mount the sda1 file in tmpdir directory
mount /dev/sda0 /tmpdir mount the sda0 file in tmpdir directory
unmount /tmpdir/boot unmount boot directory
unmount /tmpdir unmunt tmpdir directory

sync

Sync the changed or changes take effect

top

Will show the running process list

gnome-system-monitor

Show the graphical mode of running process

uptime

Show how long the system is running from last boot and
load average of first no show the the total load in last one minute

load average of second no show the the total load in last five minute
load average of third no show the the total load in last fifteen minute