Linux World

Linux Means ?

Linux is, in simplest terms, an operating system. It is the software on a computer that enables applications and the computer operator to access the devices on the computer to perform desired functions. The operating system (OS) relays instructions from an application to, for instance, the computer’s processor. The processor performs the instructed task, then sends the results back to the application via the operating system.

Explained in these terms, Linux is very similar to other operating systems, such as Windows and OS X.

But something sets Linux apart from these operating systems. The Linux operating system represented a $25 billion ecosystem in 2008. Since its inception in 1991, Linux has grown to become a force in computing, powering everything from the New York Stock Exchange to mobile phones to supercomputers to consumer devices.

Over 1,000 developers, from at least 100 different companies, contribute to every kernel release. In the past two years alone, over 3,200 developers from 200 companies have contributed to the kernel–which is just one small piece of a Linux distribution.

Basic Linux Commands

  adduser  Add a user to the system
  addgroup Add a group to the system
  alias    Create an alias •
  apropos  Search Help manual pages (man -k)
  apt-get  Search for and install software packages (Debian/Ubuntu)
  aptitude Search for and install software packages (Debian/Ubuntu)
  aspell   Spell Checker
  awk      Find and Replace text, database sort/validate/index
b
  basename Strip directory and suffix from filenames
  bash     GNU Bourne-Again SHell
  bc       Arbitrary precision calculator language
  bg       Send to background
  break    Exit from a loop •
  builtin  Run a shell builtin
  bzip2    Compress or decompress named file(s)
c
  cal      Display a calendar
  case     Conditionally perform a command
  cat      Display the contents of a file
  cd       Change Directory
  cfdisk   Partition table manipulator for Linux
  chgrp    Change group ownership
  chmod    Change access permissions
  chown    Change file owner and group
  chroot   Run a command with a different root directory
  chkconfig System services (runlevel)
  cksum    Print CRC checksum and byte counts
  clear    Clear terminal screen
  cmp      Compare two files
  comm     Compare two sorted files line by line
  command  Run a command - ignoring shell functions •
  continue Resume the next iteration of a loop •
  cp       Copy one or more files to another location
  cron     Daemon to execute scheduled commands
  crontab  Schedule a command to run at a later time
  csplit   Split a file into context-determined pieces
  cut      Divide a file into several parts
d
  date     Display or change the date & time
  dc       Desk Calculator
  dd       Convert and copy a file, write disk headers, boot records
  ddrescue Data recovery tool
  declare  Declare variables and give them attributes •
  df       Display free disk space
  diff     Display the differences between two files
  diff3    Show differences among three files
  dig      DNS lookup
  dir      Briefly list directory contents
  dircolors Colour setup for `ls'
  dirname  Convert a full pathname to just a path
  dirs     Display list of remembered directories
  dmesg    Print kernel & driver messages
  du       Estimate file space usage
e
  echo     Display message on screen •
  egrep    Search file(s) for lines that match an extended expression
  eject    Eject removable media
  enable   Enable and disable builtin shell commands •
  env      Environment variables
  ethtool  Ethernet card settings
  eval     Evaluate several commands/arguments
  exec     Execute a command
  exit     Exit the shell
  expect   Automate arbitrary applications accessed over a terminal
  expand   Convert tabs to spaces
  export   Set an environment variable
  expr     Evaluate expressions
f
  false    Do nothing, unsuccessfully
  fdformat Low-level format a floppy disk
  fdisk    Partition table manipulator for Linux
  fg       Send job to foreground
  fgrep    Search file(s) for lines that match a fixed string
  file     Determine file type
  find     Search for files that meet a desired criteria
  fmt      Reformat paragraph text
  fold     Wrap text to fit a specified width.
  for      Expand words, and execute commands
  format   Format disks or tapes
  free     Display memory usage
  fsck     File system consistency check and repair
  ftp      File Transfer Protocol
  function Define Function Macros
  fuser    Identify/kill the process that is accessing a file
g
  gawk     Find and Replace text within file(s)
  getopts  Parse positional parameters
  grep     Search file(s) for lines that match a given pattern
  groups   Print group names a user is in
  gzip     Compress or decompress named file(s)
h
  hash     Remember the full pathname of a name argument
  head     Output the first part of file(s)
  help     Display help for a built-in command •
  history  Command History
  hostname Print or set system name
i
  id       Print user and group id's
  if       Conditionally perform a command
  ifconfig Configure a network interface
  ifdown   Stop a network interface
  ifup     Start a network interface up
  import   Capture an X server screen and save the image to file
  install  Copy files and set attributes
j
  join     Join lines on a common field
k
  kill     Stop a process from running
  killall  Kill processes by name
l
  less     Display output one screen at a time
  let      Perform arithmetic on shell variables •
  ln       Make links between files
  local    Create variables •
  locate   Find files
  logname  Print current login name
  logout   Exit a login shell •
  look     Display lines beginning with a given string
  lpc      Line printer control program
  lpr      Off line print
  lprint   Print a file
  lprintd  Abort a print job
  lprintq  List the print queue
  lprm     Remove jobs from the print queue
  ls       List information about file(s)
  lsof     List open files
m
  make     Recompile a group of programs
  man      Help manual
  mkdir    Create new folder(s)
  mkfifo   Make FIFOs (named pipes)
  mkisofs  Create an hybrid ISO9660/JOLIET/HFS filesystem
  mknod    Make block or character special files
  more     Display output one screen at a time
  mount    Mount a file system
  mtools   Manipulate MS-DOS files
  mtr      Network diagnostics (traceroute/ping)
  mv       Move or rename files or directories
  mmv      Mass Move and rename (files)
n
  netstat  Networking information
  nice     Set the priority of a command or job
  nl       Number lines and write files
  nohup    Run a command immune to hangups
  notify-send  Send desktop notifications
  nslookup Query Internet name servers interactively
o
  open     Open a file in its default application
  op       Operator access
p
  passwd   Modify a user password
  paste    Merge lines of files
  pathchk  Check file name portability
  ping     Test a network connection
  pkill    Stop processes from running
  popd     Restore the previous value of the current directory
  pr       Prepare files for printing
  printcap Printer capability database
  printenv Print environment variables
  printf   Format and print data •
  ps       Process status
  pushd    Save and then change the current directory
  pwd      Print Working Directory
q
  quota    Display disk usage and limits
  quotacheck Scan a file system for disk usage
  quotactl Set disk quotas
r
  ram      ram disk device
  rcp      Copy files between two machines
  read     Read a line from standard input •
  readarray Read from stdin into an array variable •
  readonly Mark variables/functions as readonly
  reboot   Reboot the system
  rename   Rename files
  renice   Alter priority of running processes
  remsync  Synchronize remote files via email
  return   Exit a shell function
  rev      Reverse lines of a file
  rm       Remove files
  rmdir    Remove folder(s)
  rsync    Remote file copy (Synchronize file trees)
s
  screen   Multiplex terminal, run remote shells via ssh
  scp      Secure copy (remote file copy)
  sdiff    Merge two files interactively
  sed      Stream Editor
  select   Accept keyboard input
  seq      Print numeric sequences
  set      Manipulate shell variables and functions
  sftp     Secure File Transfer Program
  shift    Shift positional parameters
  shopt    Shell Options
  shutdown Shutdown or restart linux
  sleep    Delay for a specified time
  slocate  Find files
  sort     Sort text files
  source   Run commands from a file `.'
  split    Split a file into fixed-size pieces
  ssh      Secure Shell client (remote login program)
  strace   Trace system calls and signals
  su       Substitute user identity
  sudo     Execute a command as another user
  sum      Print a checksum for a file
  symlink  Make a new name for a file
  sync     Synchronize data on disk with memory
t
  tail     Output the last part of files
  tar      Tape ARchiver
  tee      Redirect output to multiple files
  test     Evaluate a conditional expression
  time     Measure Program running time
  times    User and system times
  touch    Change file timestamps
  top      List processes running on the system
  traceroute Trace Route to Host
  trap     Run a command when a signal is set(bourne)
  tr       Translate, squeeze, and/or delete characters
  true     Do nothing, successfully
  tsort    Topological sort
  tty      Print filename of terminal on stdin
  type     Describe a command •
u
  ulimit   Limit user resources •
  umask    Users file creation mask
  umount   Unmount a device
  unalias  Remove an alias •
  uname    Print system information
  unexpand Convert spaces to tabs
  uniq     Uniquify files
  units    Convert units from one scale to another
  unset    Remove variable or function names
  unshar   Unpack shell archive scripts
  until    Execute commands (until error)
  useradd  Create new user account
  usermod  Modify user account
  users    List users currently logged in
  uuencode Encode a binary file
  uudecode Decode a file created by uuencode
v
  v        Verbosely list directory contents (`ls -l -b')
  vdir     Verbosely list directory contents (`ls -l -b')
  vi       Text Editor
  vmstat   Report virtual memory statistics
w
  watch    Execute/display a program periodically
  wc       Print byte, word, and line counts
  whereis  Search the user's $path, man pages and source files for a program
  which    Search the user's $path for a program file
  while    Execute commands
  who      Print all usernames currently logged in
  whoami   Print the current user id and name (`id -un')
  Wget     Retrieve web pages or files via HTTP, HTTPS or FTP
  write    Send a message to another user
x
  xargs    Execute utility, passing constructed argument list(s)
  yes      Print a string until interrupted
  .        Run a command script in the current shell
  ###      Comment / Remark



How To Edit Grub Boot Parameters

The reason that you will usually want to change boot parameters is to configure the default kernel to something specific to your hardware. Grub allows you to change a boot parameter temporarily , in which case it won't survive a system reboot, or permanently, which means that it will. When trying to fix something on your machine using kernel parameters, a reasonably safe way to proceed is to first make the changes temporarily, check that you get what you expect, and then make the change permanent. If changing kernel boot parameters sound scary, it isn't. None of the boot parameters that I have come across are destructive in any way. The worst result could be that your machine hangs until you restart it. Even if you make the change permanently, you always still have the opportunity of intercepting the Grub boot and changing the parameter back. 1. Changing Boot Parameters Temporarily Generally, this is used when you want to try a parameter change to see it is beneficial to your system. When the PC boots up, you will see the Grub countdown, which is set to 3 seconds by default. Press "Esc" to intercept this countdown and go enter a Grub menu. Then
  • Press 'e' to start editing.
  • Scroll down to the "kernel..." line. The is the line that tells Grub which kernel to boot with and the parameters to be passed to the kernel when it boots are placed at the end of this line.
  • Press 'e' again to edit this line.
  • Move to the end of the line. You will see any existing parameters and can add other new parameters to the end.
  • Parameters are separated by spaces and are mostly either a single word (e.g. nolapic), or an equation (e.g. acpi=off).
  • Once you have added the parameter to the end of the line, press Enter to accept the editing.
  • Then press 'b' to boot using that kernel and those parameters.
Remember, this change is not permanent. At next boot, it will be undone. 2. Making Boot Parameter Changes Permanent Assuming that you booted with a new or changed parameter and would now like to make this a more permanent change, you need to edit the file that contains these settings. This file (/boot/grub/menu.lst) is owned by root and, therefore, requires root privileges to edit. There are a number of ways to do this depending on your editor of choice. For me
sudo vi /boot/grub/menu.lst
works. If you are not familiar with vi, then it might by something along the lines of
gksudo gedit /boot/grub/menu.lst
will edit this file in the Ubuntu gedit graphical text editor. Now, there are two flavours of permanent to consider. The first is to make the change survive reboots, the second is to survive an upgrade. 2.1 Making a change survive reboots Find the section shown below. The details will vary depending on which kernel(s) are installed on your machine.
## ## End Default Options ## title Ubuntu, kernel 2.6.20-15-generic root (hd0,0) kernel /boot/vmlinuz-2.6.20-15-generic root=UUID=fccafcc7-d7cc-4594-9459-a8f0db7b9f7f ro quiet splash initrd /boot/initrd.img-2.6.20-15-generic quiet savedefault
Add your parameters to the end of the line starting with "kernel...". This should be the same line that you would edit in the temporary change scenario above. Save the file and the change will survive a reboot.
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