sudo dpkg -i DEB_PACKAGE

sudo dpkg -r PACKAGE_NAME

sudo apt-get install libxss1 libappindicator1 libindicator7
wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb
sudo dpkg -i google-chrome*.deb

Source:\\http://superuser.com/questions/176783/what-is-the-difference-between-executing-a-bash-script-and-sourcing-a-bash-scrip/176788#176788
Consider following script pid.sh:

#!/bin/sh
echo $$

(the special variable $$ expands to the PID of the current running shell process)

First print the PID of the current shell:

$ echo $$
25009

Source the script:

$ source pid.sh
25009

Execute the script, note the PID:

$ ./pid.sh
25011

Source again:

$ source pid.sh
25009

Execute again:

$ ./pid.sh
25013

You can see that sourcing the script runs in the same process while executing the script creates a new process everytime. That new process is the new shell which was created for the execution of the script. Sourcing the script does not create a new shell and thus the PID stays the same.

Summary

Both sourcing and executing the script will run the commands in the script line by line, as if you typed those commands by hand line by line.

The differences are:

- When you execute the script you are opening a new shell, type the commands in the new shell, copy the output back to your current shell, then close the new shell. Any changes to environment will take effect only in the new shell and will be lost once the new shell is closed.

- When you source the script you are typing the commands in your current shell. Any changes to the environment will take effect and stay in your current shell.

Use source if you want the script to change the environment in your currently running shell. Use execute otherwise.

#! test.sh
echo hola
exit

a) cambiar exit por return y ejecutar con source o . (punto) b) ejecutar con sh

sh test.sh

lsof -i :3000

notifying all users prior to shutdown as in:

$ sudo shutdown -h 10:00 "Shutting down for scheduled maintenance."

shutdown -h
halt
poweroff

shutdown -r
reboot

Folders: /bin, /usr/bin,/sbin,/usr/sbin, /opt.

$ which diff
$ whereis diff

locate & find

Searching for files and directories named “gcc”:

$ find /usr -name gcc

Searching only for directories named “gcc”:

$ find /usr -type d -name gcc

Searching only for regular files named “test1”:

$ find /usr -type f -name test1

Finding based on time:

$ find / -ctime 3

Finding based on size

$ find / -size +10M

$ find ./uploads -iname "taller*" -type f -exec cp -p {} /home/alfredo/projects/shk/app/assets/images/fondos/ \;

? Matches any single character * Matches any string of characters [set] Matches any character in the set of characters, for example [adf] will match any occurrence of “a”, “d”, or “f” [!set] Matches any character not in the set of characters

To find and remove all files that end with .swp:

$ find -name "*.swp" -exec rm {} ’;’

tree -d

To see mounted fs permissions

mount

To see static file system information

cat /etc/fstab

df -Th

NFS service

sudo service nfs start

Text file with shared folders and permissions

# /etc/exports
/projects *.example.com(rw)

Soft restart

exportfs -av

Permanent: In file /etc/fstab

servername:/projects /mnt/nfs/projects nfs defaults 0 0

One time:

mount servername:/projects /mnt/nfs/projects

/proc

/proc/cpuinfo
/proc/interrupts
/proc/meminfo
/proc/mounts
/proc/partitions
/proc/version

You can use the following utilities to view files:
Command Usage
cat Used for viewing files that are not very long; it does not provide any scroll-back.
tac Used to look at a file backwards, starting with the last line.
less Used to view larger files because it is a paging program; it pauses at each screenful of text, provides scroll-back capabilities, and lets you search and navigate within the file. Note: Use / to search for a pattern in the forward direction and ? for a pattern in the backward direction.
tail Used to print the last 10 lines of a file by default. You can change the number of lines by doing -n 15 or just -15 if you wanted to look at the last 15 lines instead of the default.
head The opposite of tail; by default it prints the first 10 lines of a file.

echo string > newfile  The specified string is placed in a new file.
echo string >> existingfile   The specified string is appended to the end of an already existing file.
echo $variable  The contents of the specified environment variable are displayed.

cat file1 file2 Concatenate multiple files and display the output; i.e., the entire content of the first file is followed by that of the second file.
cat file1 file2 > newfile Combine multiple files and save the output into a new file.
cat file >> existingfile Append a file to the end of an existing file.
cat > file   Any subsequent lines typed will go into the file until CTRL-D is typed.
cat >> file   Any subsequent lines are appended to the file until CTRL-D is typed.

$ ln -s file1 file4
$ ls -li file1 file4

To push current folder to the stack

pushd .

To list the stach

dirs

To change to the last pushed folder

popd

stdin ⇒ descriptor 0 (usu keyboard) stdout ⇒ descriptor 1 (usu screen) stderr ⇒ descriptor 2 (screen or file)

$ do_something > output-file

stdout goes to 'output-file' file, stderr goes to screen (by default)

$ do_something 2> error-file

stdout goes to screen (by default) stderr (file descriptor 2) goes to 'error-file' file

$ do_something >& all-output-file
$ do_something > all-output-file 2>&1

stdout and stderr goes to 'all-output-file' file

Essential programs

/bin

Non-essential binaries

/usr/bin

System administration binaries

/sbin

Device nodes

/dev

Variable files

/var
  System log files: /var/log
  Packages and database files: /var/lib
  Print queues: /var/spool
  Temp files: /var/tmp
  FTP service: /var/ftp 
  HTTP web service: /var/www

System configuration files, global settings for all users

/etc

resolv.conf: where to go on the network to obtain host name to IP address mappings (DNS)
passwd, shadow, group: for managing user accounts 
rc2.d: (System run level scripts) contains links to scripts for entering and leaving run level 2

Boot

/boot

  vmlinuz: the compressed Linux kernel, required for booting
  initramfs: the initial ram filesystem, required for booting, sometimes called initrd, not initramfs
  config: the kernel configuration file, only used for debugging and bookkeeping
  System.map: kernel symbol table, only used for debugging
  grub: grand unified bootloader

Libraries

/lib
/lib64

Removable devices (CS, USB, DVD; …)

/media

Other

/opt  Optional application software packages.
/sys  Virtual pseudo-filesystem giving information about the system and the hardware. Can be used to alter system parameters and for debugging purposes. 
/srv  Site-specific data served up by the system. Seldom used.
/tmp  Temporary files; on some distributions erased across a reboot and/or may actually be a ramdisk in memory.
/usr  Multi-user applications, utilities and data.

diff <file1> <file2>
  -c listing of differences that include 3 lines of context before and after the lines differing in content
  -r recursively compare subdirectories as well as the current directory
  -i Ignore the case of letters
  -w Ignore differences in spaces and tabs (white space)

diff3 MY-FILE COMMON-FILE YOUR-FILE

Create the patch (the diferences only)

diff -Nur originalfile newfile > patchfile

Apply a patch to directory (see man patch)

patch -p1 < patchfile

Apply a patch to a file

patch originalfile patchfile

Windows → by file extension

Linux → by file contents =⇒ file utility

rsync -r project1 archive-machine:projects/project1

Options
-r recursive
-dry-run do-no execute

gzip
bzip2
xz
zip

tar zcvf file.tar.gz * -> join and copmress files in current folder and subfolders and copmress it with gzip
tar xf file.tar.gz -> decompress and restores file.tar.gz in current folder

tar -zcvfp filename.tar.gz files

z uses gzipc creates new filev verbosef specifies where to put the new compression (filename.tar.gz)p preserves permissions

tar -xvpzf filename.tar

tar -xvpzf filename.tar -C path_to_folder

tar -ztvf filename.tar.gz

dd

Copiar backups automáticos de Nairobi

scp -r alfredo@nairobi.pres.in:/home/alfredo/backups/database/postgresql/* /home/alfredo/backups/remote/

Copiar fotos de uploads:

scp -r alfredo@nairobi.pres.in:/home/alfredo/rails_apps/shk/shared/public/uploads /home/alfredo/projects/shk/public

CTRL+R reverse search
!! last command
!n n-th last command
!$ last parameter in the last command
!string last command starting with string

        TASK
CTRL-L  Clears the screen
CTRL-D  Exits the current shell
CTRL-Z  Puts the current process into suspended background
CTRL-C  Kills the current process
CTRL-H  Works the same as backspace
CTRL-A  Goes to the beginning of the line
CTRL-W  Deletes the word before the cursor
CTRL-U  Deletes from beginning of line to cursor position
CTRL-E  Goes to the end of the line
Tab   Auto-completes files, directories, and binaries

$ alias --> list of alias

~/.bashrc

alias <name>='<command>'

chown

chgrp

The permission in the command line is displayed as: _rwxrwxrwx 1 owner:group

- rwx rwx rwx 1 owner:group
d = directorio
  owner
      group
          others
              hardlinks to the file

chmod <permissions> <file>

Permissions:

u/g/o +- r/w/x
numérico binario

Ejemplo:

chmod 755 file1  -->  -rwxr-xr-x

Si file1 tiene -rw-rw-r–

chmod uo+x,g-w file1 --> -rwxr--r-x

Usage:

ipcalc [options] <ADDRESS>[[/]<NETMASK>] [NETMASK]

ipcalc takes an IP address and netmask and calculates the resulting broadcast, network, Cisco wildcard mask, and host range. By giving a second netmask, you can design sub- and supernetworks. It is also intended to be a teaching tool and presents the results as easy-to-understand binary values.

Host name

hostname

IP address and other informaiton

host <name>
nslookup <name>

Network adapters

ifconfig

Debian

cat /etc/network/interfaces
/etc/init.d/networking start

Fedora

cat /etc/sysconfig/network
cat /etc/sysconfig/network-scripts/ifcfg-eth0

ip addr show
ip route show
ping <hostname>
route -n
route add/del -net address
traceroute <hostname>

ethtool   Queries network interfaces and can also set various parameters such as the speed.
netstat   Displays all active connections and routing tables. Useful for monitoring performance and troubleshooting.
nmap  Scans open ports on a network. Important for security analysis
tcpdump   Dumps network traffic for analysis.
iptraf  Monitors network traffic in text mode.

Source: http://bencane.com/2013/02/25/10-nmap-commands-every-sysadmin-should-know/

nmap -sP 192.168.1.0/24 ==> discovers IP addresses
nmap 192.168.1.0/24     ==> scan for open ports in the whole net
nmap -O 192.168.1.50    ==> Identify the Operating System of a host (requires root)
nmap -sL 192.168.1.0/24 ==> Identify Hostnames
nmap -sS -sU -PN 192.168.1.50 ==> TCP Syn and UDP Scan (requires root)
nmap -T4 -F 192.168.1.50      ==> Fast scan for open ports (100 most common)
nmap -T4 -A 192.168.1.0/24    ==> Agressive scan for open ports

nmap -v ...  ==> verbose command

ssh-keygen
ssh-copy-id remote-host