A collection of Linux commands and concepts I tend to forget
A. System
#reboot
sudo reboot
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
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
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. 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 withMYUSER
- Reload SSH with
sudo reload ssh
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
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