advanced-linux

Repository for advanced linux knowledge such as important commands, files etc.

Commands

cal

Shows calendar

cat file_name

Shows file content

cd folder

Changes directory

Quick Folders:

• ~ user's directory
• ~ myuser myuser's directory
• . current directory
• .. parent directory

clear

Clears current terminal screen

cp source target

Copies the file

cp -R source target

Copies the directory

date

Shows system time

echo string

Prints string

echo string > file_name

Write string in file (no check for content, overwrites it)

echo string >> file_name

Appends string to file content

find directory

Search for files in a directory hierarchy

find directory -name file_name

Search for file in a directory hierarchy

find directoy -user user_name

Search for user's files in a directory

grep search_string file_name

Search in file

less file_name

Shows file content with moving features

ls

Lists content of working directory

Options:

• -l long list
• -a shows hidden content

man command

man command is used for information about commands.

mkdir directory_name

Makes a directory with given name

mv source target

Moves the file or directory

nano

nano is a command line text editor

pwd

Prints working directory

rmdir directory_name

Removes the directory

rm file_name

Removes the file

rm -f file_name

Removes the file forcely

rm -i file_name

Asks for removing file

rm -r file_name

Remove with child directories (recursive)

touch file_name

Creates a blank file

uname

Shows the operating system name

uname -a

Shows the detailed operating system information (eg. distribution, kernel version)

Operators

command1 | command2
Executes command1 then executes command2 with command1's output

command1 > file_name
Writes command1's output (stdout) into file_name (no check, overwrites it)

command1 >> file_name
Appends command1's output (stdout) into file_name

command1 2> file_name
Writes command1's error output (stderr) into file_name

command1 2>&1
Writes command1's error output (stderr) to stdout (prints on screen)

command1 < file_name
Send file_name to command1 as input (stdin)

Command line stream codes:

• 0 : stdin
• 1 : stdout
• 2 : stderr

Some Important Files

/etc/resolv.conf           -> System DNS servers
/etc/issue                 -> Distribution version
/etc/passwd                -> Local users
/etc/shadow                -> User password summaries
/etc/sudoers               -> Sudo rules
/home/*/.bash_history      -> User command history
/home/*/.ssh/id*           -> SSH keys
/home/*/.vnc               -> VNC remote access information

Some Important Folders

/      -> Root Directory
/bin   -> User Binaries
/sbin  -> System Binaries
/etc   -> Configuration Files
/dev   -> Device Files
/proc  -> Process Information
/var   -> Variable Files
/tmp   -> Temporary Files
/usr   -> User Programs
/home  -> Home Directories
/boot  -> Boot Loader Files
/lib   -> System Libraries
/opt   -> Optional add-on Apps
/mnt   -> Mount Directory
/media -> Removable Devices
/srv   -> Service Data

Compressing

There are 3 different methods for compressing

compress (extension .Z)
compress - compressing
uncompress - uncompressing

gzip (extension .gz)
gzip - compressing
gunzip - uncompressing

bzip2 (extension .bz2)
bzip2 - compressing
bunzip2 - uncompressing

Compressing with tar

Creating archives

tar -zcvf archive.tar.gz file1 file2
Explaining parameters

• -z for zip
• -c for create
• -v for verbose (graphical output)
• -f for file

Extracting archives

tar -zxvf archive.tar.gz
-x parameter for extracting

Viewing files in archive

tar -ztvf archive.tar.gz
-t parameter for list content

Logs

journalctl command can be used for log informations.

Additional information can be found on journalctl manpage.

Also see

https://devhints.io/bash