A. System

## 0.README-Linux-Command-Line-Cheat-Sheet.md

      
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              0.README-Linux-Command-Line-Cheat-Sheet.md
            
          
    A collection of Linux commands and concepts I tend to forget

  
## A.system.md

      
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              A.system.md
            
          
    A. System
#reboot
sudo reboot

  
## B.file-system.md

      
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              B.file-system.md
            
          
    B. File System
Info
Current directory: pwd

Show file contents: cat File
List file sizes: ls -lah
Log file viewing: tail error_log -n 50
List size of all directories in current directory: find . -maxdepth 1 -type d | xargs du -m -s
Find files
find . -name '*{part_of_word}*' -print
What is taking up space?
cd /
du -ch -d 1 | sort -hr
...or ncdu
more
Free disc space: df -h

Directory size: du -sh /var
Removing old kernel images etc.
sudo apt-get autoremove
Creating Archives
zip -r foo.zip dir_path

Extracting Archives
unzip .zip-file-name -d /path/to/extract


## C.permissions.md

      
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              C.permissions.md
            
          
    C. Permissions
There are three permissions you can set, and there are three classes that can receive those permissions.
read, write, execute
user, group, others

Symbolic Notation	Octal Notation	English
----------	0000	no permissions
---x--x--x	0111	execute
--w--w--w-	0222	write
--wx-wx-wx	0333	write & execute
-r--r--r--	0444	read
-r-xr-xr-x	0555	read & execute
-rw-rw-rw-	0666	read & write
-rwxrwxrwx	0777	read, write, & execute


#list users
cat /etc/passwd

#list groups
cat /etc/group


Each user usually has at least one corresponding group, which has the same name as the user.


Directories are just special files, and they have the same owner and permission rules as ordinary files.


## D.users.md

      
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              D.users.md
            
          
    D. User handling
Change password
passwd
Create user
sudo adduser MYUSER
Allow user to login over SSH

Edit SSH configuration: sudo vim /etc/ssh/sshd_config
Add AllowUsers MYUSER to the bottom of the file to only allow ssh login with MYUSER
Reload SSH with sudo reload ssh


## E.activity.md

      
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              E.activity.md
            
          
    E. System Activity and Resources
Find process
ps -ef | grep php
Top
top
displays memory usage: Shift + f, then press n

Understanding Load avarages - good article by Scout App

Free
free - shows available memory
http://stackoverflow.com/questions/3784974/want-to-know-whether-enough-memory-is-free-on-a-linux-machine-to-deploy-a-new-ap/4417121#4417121
Explaination: http://www.linuxatemyram.com/
free -m


To see how much ram is free to use for your applications, run free -m and look at the row that says "-/+ buffers/cache" in the column that says "free". That is your answer in megabytes:

see also http://www.cyberciti.biz/faq/linux-check-memory-usage/
Network monitoring
sudo iftop
sudo nethogs eth0

Articles

http://www.cyberciti.biz/tips/top-linux-monitoring-tools.html
https://www.digitalocean.com/community/community_tags/monitoring