Before studying the command line, we should know something about linux and ubuntu.

Linux

Linux is a Unix-like computer operating system assemble under the model of free and open-source software development and distribution, the defining component of linux is the linux kernel.(from Wikipedia)

Ubuntu

Ubuntu is a Debian-based Linux operating system for personal computer, tables and smartphones, where Ubuntu Touch Edition is used.
Ubuntu this word is also based on free software and named after the Southern African philosophy of ubuntu,
can be translated as "humanity to others" or "I am what I am because of who we all are".

** Commitment of Ubuntu**
It is the essential reasons for the success of Ubuntu.

• Ubuntu is free forever, including commercial distrubution and security update.
• Ubuntu is provided business support by Canonical and global hundreds of companies.
• Ubuntu has the free software communtiy, which provides the best translation and barrier-free facilities.
• The Ubuntu is publicly committed to the principles of open source software development ; people are encouraged to use free software, study how it works, improve upon it, and distribute it.

Command line

Linux command is to supervise and control the Linux system. The commonly used command are as follows.

cd——Change Directory

cd        -enter main directory
cd /home  -enter '/home'  directory
cd ..     - return to higher level directory

pwd——Print Working Directory

ls——List

ls        -list the files in the directory
ls -f     -classify the directory and files
ls -l     -list detail of the files and directory
ls -a     -list the hidden files

mkdir——Make Directory

mkdir dir1         -make a directory named dir1
mkdir dir1 dir2    -make two directory

rm——remove files

rmdir——remove directory

rm -f file1    -remove a file named file1
rmdir dir1     -remove dir1 directory if it's empty
rm -rf dir1    -remove dir1 directory and its contents

cp——copy files

cp file1 directory  -copy file1 to  directory
cp -a dir1 dir2     -copy a directory

mv——move

mv dir1 new_dir   -rename or remove to another directory

tar

tar -cvf archive.tar file1              -create a incompressible tarball
tar -cvf archive.tar file1 file2 dir1   -create a archive file including file1 file2 and dir1
tar -tf archive.tar                     -show a tarball content
ar -xvf archive.tar                     -decompress a tarball
tar -xvf archive.tar -C /tmp            -decompress a tarball on the tmp
 tar -cvfj archive.tar.bz2 dir1         -create a bzip2 format tarball
tar -xvfj archive.tar.bz2               -decompress a bzip2 format tarball
 tar -cvfz archive.tar.gz dir1          -create a gzip format tarball
 tar -xvfz archive.tar.gz               -decompress a gzip format tarball

zip

zip file1.zip file1    -create a zipball
zip -r file1.zip file1 file2 dir1 
unzip file1.zip        -decompress a zipball

grep

grep string1 file1       -search string1 in file1
grep -i string1 file1    -search string1 in file1 ignore case

tail

tail file1      -cat last 10 line of file1
tail -n file1   -cat last 2 lien of file1

su

su user1   -switch user

apt-get

apt-get install package_name       -install or update a deb package
apt-get update                     -update deb packages in the list
apt-get upgrade                    -upgrade all the installed package
apt-get remove package_name        -remove a package form system
apt-get clean                      -clean cache from the software package

ps :show the operating processes

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