EmbLogic » debian

ls – list command

Ankur Garg — Wed, 10 Feb 2016 17:20:32 +0000

ls – list command
=================
- ls means list directory content
- Prototype :
ls [OPTION] … [FILE] …
- Exit status
It returns 0 ,on success
Returns 1 in case of minor problems (eg. cannot access subdirectory)
returns 2 in case of serious trouble (eg. Cannot access command line argument)
- For specific listing you can use *
eg.1) For listing all files starting with a use :
ls a*
2) for listing all .c files use :
ls *.c
3) for listing all .c files starting with a use :
ls a*.c
- Some common options are :
i) -a –all –> Do not ignore enteries starting with .
Use this to view swap or temporary files.
ii) -l –> long listing format
iii) -r –) Reverse order sort (by name) and list
iv) -s –size –> Print allocated size of each file in blocks
v) -S –> Sort by file size
vi) -t –> Sort by modification time, newest first
vii) -U –> Do not sort; list enteries in directory order
viii) -X –> Sort alphabetically by entry extension.
ix) -F –> to distinguish files from directories (Puts / in directory and * with executable files)
x) -R –> It shows files that are contained in directory. It continued to dirrectory in a directory and so on.

- In fedora for long lsting use command :

CD – Change Directory Command

Ankur Garg — Wed, 10 Feb 2016 17:18:28 +0000

CD – Change Directory Command
=============================
- cd means change working directory
- Prototype:
cd [-L | -P] [directory]
cd -
-If you do not give any directory to cd command, it will take you to home directory.
eg. cd –> It will go to home directory.
- For previous directory use :
cd ..
- Further for more than one previous directory use :
cd ../..
- Directory can be defined by 2 types :
i) Absolute filepath – Path starting from ‘/’.
eg. cd /usr/bin/
ii)Relative Filepath – Path relative to current directory
eg. cd /usr –> Absolute filepath
cd etc –> Relative Filepath

Common linux virtual directories

Ankur Garg — Tue, 09 Feb 2016 15:00:57 +0000

Common Linux Virtual Directories
=================================
Directory Usage
/ Root of virtual directory. No files are placed here (normally)
/bin Binary directory.GNU user level utilities are stored
/boot Boot directory.Boot files are stored here
/dev device directory, where linux creates device nodes
/etc system configuration files directory
/home home directory, user directories are placed here
/lib System & application library files are stored here
/media Common place for mount point of removable media
/mnt mount directory, for removable devices
/opt used to store optional software packages
/root home directory of root user
/sbin GNU admin level utilities are store here
/tmp Temporary work files are created and destroyed
/usr User installed softwares directory
/var For frequently changing directory ,such as log files

Linux Run Levels

Ankur Garg — Tue, 02 Feb 2016 12:36:51 +0000

Linux Run Levels
================
Run Level   Description
0      Halt
1         Single-User mode
2      Multi-user mode, usually without networking support
3          Full multi-user mode with networking
4          Unused
5      Multiuser mode with networking and a graphical X window Session
6          Reboot

- To change run level use init command

init run_level
- Most normal is run level 5 for graphical linux system.
- Level 1 is used for troubleshooting or emergency purpose.
- Most linux softwares start the network softwares at run level 3.
- What aplications work at Run level is determined by system by RC script.

Boot process of linux

Ankur Garg — Tue, 02 Feb 2016 12:27:09 +0000

The boot process of linux
=========================
- After you turn on your Linux System, linux kernel loads into memory and runs.
- Firstly, it runs the init process.
- init program is usually located at /sbin/init.
- init process has PID 1.
- The init process then starts all other processes.
- The init process reads the /etc/inittab file during boot (This is outdated now).