about:cache = type this in firefox url and it gives cache size
alias = lists aliases
apropos php = info about php modules
alsactl -v = prints alsa mixer’s version
amixer = info about amixer component
amixer info = info about amixer
amixer -c = available amixer controls
anacron -v = version of anacron
aplaymidi -v = version of aplay
apm -v = version of apm
apropos php = info about all php modules
arecord -v = version of arecord
bc = starts a command line calculator
cal = shows calendar
cal 2009 = shows 2009 calendar
cal -j = prints current month’s calendar where days are numbered
cal -m = pritns current month’s calendar where Monday is the 1st day
cal -y = prints current year’s calendar
cal 12 2005 = prints December month of 2005
cat /var/log/yum.log
cat /var/log/yum.log | grep mysql = mysql install and update dates
cat /proc/meminfo = prints memory info
cat /proc/cpuinfo = prints cpu info
cat /proc/devices = list of devices
cat /proc/statistics = disk statictics
cat /proc/filesystems = file system info
cat /proc/interrupts = IRQ channel assignments
cat /proc/iomem = physical memory addresses
cat /proc/ioport = virtual memory addresses
cat /proc/keys = list of keys kept by kernel
cat /proc/loadavg = shows 1 5 15 min load averages
cat /proc/misc = list of devices
cat /proc/modules = list of loaded modules
cat /proc/mounts = list of mounts
cat /proc/partitions = list of partitions
cat /proc/mdstat = RAID status
cat /proc/stat = kernel statictics
cat /proc/swaps = list of swaps
cat /proc/uptime = uptime in seconds
cat /proc/version = kernel version
cat /var/xyz.txt = prints output of a file
cat /selinux/enforce = current status of selinux
cat /etc/shells = lists all installed shells on the os
cat /etc/inittab = info about run levels
cat filename | sort = sorting output in alphabetical order
cat filename.txt | less = shows contents of the file, scroll bar fixed, q to quit
cat filename.txt | more = shows contents of the file, page by page, spacebar to another page
cat /etc/x11/xorg.conf = monitor info
cat -s filename.txt = shows consecutive blank lines as one
cat -n filename.txt = shows all lines with numbers
cat -b filename.txt = shows only none-blank lines with numbers
cat filename.txt | head = gives top 10 lines ie head of the file
cat filename1 filename2 > filename3 = merges the files
cat filename1 filename2 >> filename3 = adds contents to another files
cat /etc/fstab = list of all devices
cat /etc/filesystems = of file systems
cat /etc/fedora-release = Fedora release/version no
cat /etc/issue = Linux distro name
cat /var/log/messages | grep -F ntpd =
cat /var/log/wtmp = lists all logins and logouts
cat /run/utmp = lists last reboots and shutdowns
cat /bin/ls | strings = lists all ASCII text in ls
cat abc.txt | tr ‘[a-z]’ ‘[A-Z]’ = converts file into uppecase
cat abc.txt | tr ‘[a-z]’ ‘[A-Z]’ > uppecase.txt = converts file into a new file
cat /usr/include/asm/unistd.h = list of system calls
cat /usr/include/asm/unistd.h | wc -l = number of system calls
cd / = takes into root directory
cdrecord -scanbus = lists available cd/dvd devices
chkconfig –list mysqld = mysql configuration details
chsh username /bin/bash =
chsh -s new-shell username = change the default shell to a new one
clear = clears the screen/prompt
chmod o=rwx, g=rw, u=r /usr/local/bin = change file permissions
chmod ogu=rwx /usr/local/bin = change file permissions
convert imagename.jpg imagename.png = converts jpg image into png
convert imagename.gif imagename.bmp = converts gif image into bmp
convert imagename.tiff imagename.pcx = converts tiff image into pcx
convert -resize 340×140 image1.jpg image2.jpg = resizes jpg image
convert -sample 50%x50% image1.jpg image2.jpg = resizes jpg image
convert -rotate 90 image1.jpg image2.jpg = rotates jpg image 50 degrees
convert -fill blue -pointsize 80 -font helvetica -draw ‘text 10,50 “my image”’ img1.jpg img2.jpg = inserts text into jpg image
convert -thumbnail 120×120 a.jpg b.png = converts jpg image into png image
convert -thumbnail 120×120 -polaroid 8 a.jpg b.png = converts into polaroid picture
convert -thumbnail 120×120 -polaroid 8 -rotate 8 a.jpg a-c.png = converts and rotates
convert -sepia-tone 75% imga.jpg imgb.png = changes tone of image
convert -charcoal 5 house.jpg char-house.png = changes tone of image
convert -colorize 175 house.jpg color-house.png = changes color of image
Ctrl+Alt+delete = restarts Linux
Ctrl+Alt+backspace = restarts login screen
Ctrl+Shift+Ins(Insert) = pasting something from other source ie web page etc to command prompt
Ctrl+C = clear the command line if the output keeps running…..
date = prints today’s date
date ‘+%A %B %d %G’ = display day, month, day of month, year
date ‘+The date today is %F.’ = displays date in yyyy-mm-dd format
date –date=’2 weeks’ = displays date two weeks from today
date –date=’20 days’ = displays date 20 days from today
date –date=’2 months’ = displays date 2 months from today
date –date=’2 years’ = displays date 2 years from today
date –date=’2 years 2 months 2 days’ = displays date 2 years 2 months 2 days from today
date –date=’14 Jul’ +%A = display day on which July 14 falls
diff oldfile.txt newfile.txt = checks difference between two files
dig yahoo.com = gives info about yahoo website
dmesg = a summary of hardware profile
dmesg | head n -5 = shows first 5 lines
dmesg | head -5 = shows first 5 lines
dmesg | tail -n 4 = shows last 4 lines
dmesg | tail -4 = shows last 4 lines
dmesg | grep ATA = shows lines containing ATA
dmidecode = BIOS info
dmidecode | head -n10 = first 10 lines of BIOS info
dmidecode –-type baseboard = baseboard info
dmidecode –-type cache = cache info
dmidecode –-type chassis = chassis info
dmidecode –-type connector = connector info
dmidecode –-type memory = memory info
dmidecode –type processor = processor info
dmidecode –-type slot = slot info
dmidecode –-type system = system info
dmidecode –-type wrongtype = gives right words/types
dos2unix abc.txt xyz.txt = converts file into unix format