Useful Linux Tips for Web App Engineer



Linux Command Line(Cover All Essential Linux Commands)

I read the book “Linux Command Line (Cover All Essential Linux Commands)“.
There are a lot of useful Tips in Linux. I would like to show some of them from the book!


👽 Filesystem

I have never seen the following meanings of Linux drectories.
It is so good for me!

  • /bin : Basic command line utilities for all users
  • /boot : Commands to boot on computer
  • /dev : All devices files
  • /etc : A set of system configuration
  • /home : Users’ data files
  • /lib : Program libraries
  • /mnt : Mount point of removable various devices
  • /opt : Optional files and packages loaded onto the system
  • /sbin : System administration commands
  • /tmp : Temporary files
  • /usr : Programs and data available to all users
  • /proc : All kernel-related processes
  • /root : Superusers’ home directory
  • /var : Variable data like system logs, prit spool files and etc.

🐠 Linux Symbols

  • < : Get input from afile to a command
  • > : Send output from a command to file
  • >> : Append output a file
$ cat file1.txt >> file2.txt
  • | : Send cmd1 output to cmd2 input
$ ls -al /etc | less
  • ; : Combile two or more commands
  • \ : Escape the special character
  • ./ : Run a script in the current directory
  • .. : Parent directory
  • ~ : Home direcotory
  • $ : Variable prefix for valiable name and value
  • $$ : Show the running processes number
  • !! : Repeat the last command
  • !string : Run recent cmd that begins with string
$ !cat

🐰 Access Permissions

rwx signify the access permissions which can be described by a number from 1 to 7.

  • 4(r) : Read Permissions
  • 2(w) : Write Permissions
  • 1(x) : Execute Permissions

Access permissions for a file are devided in to three:

  • User Permissions
  • Group Permissions
  • Others Permissions

🎂 About Run Levels

  • Level 0 : Halt-the system is in the process of shutting down
  • Level 1 : Single-user mode. Only small set of kernel process running
  • Level 2 : Basic Multi-user mode without network services started
  • Level 3 : Full Multi-user mode with network services started
  • Level 4 : User defined mode
  • Level 5 : Full multiuser mode with X window
  • Level 6 : System reboot

🖥 Recommended VPS Service

VULTR provides high performance cloud compute environment for you. Vultr has 15 data-centers strategically placed around the globe, you can use a VPS with 512 MB memory for just $ 2.5 / month ($ 0.004 / hour). In addition, Vultr is up to 4 times faster than the competition, so please check it => Check Benchmark Results!!