Anth's Computer Cave

Quick Linux Tips

This page has some quick tips for getting things done on Linux. These commands should work on Ubuntu, Mint and Raspbian.

GENERAL TERMINAL COMMANDS

Some commands require root permissions. To run a command as root add sudo to begining of command.


Session details and control

Swith to another user call Fred:

su Fred

To see how long the system has been running:

uptime

To see the last time the system was shut down:

sudo last -x shutdown

To exit the session:

exit


Shutting Down and Rebooting

To shut down the system imediately:

sudo shutdown now

To shut down and power off the system in two minutes:

sudo shutdown -h +2

The '-h' switch tells the system to also power off if the option is available.>/p>

To send a message to other users and shut down in 3 minutes:

sudo shutdown -h +3 "It's Going Down!!!"

Another option is:

sudo poweroff

To cancel a shutdown:

sudo shutdown -c

To reboot the system:

sudo reboot


Updating

To update your list of available packages: sudo apt-get update

To upgrade your packages: sudo apt-get upgrade

To remove old packages:sudo apt-get autoremove


Time and date

To view full time, date and timezone: date

Timezone

To change timezone: sudo dpkg-reconfigure tzdata

An ancient looking GUI window will appear. Use the arrow keys to select your timezone and press Enter


Ownership and permissions

Change file ownership and group

The chown command changes the owner and group for one or many files or folders.

Change the ownership of a file called example.txt to the user YourName and the group YourGroup:

sudo chown YourName:YourGroup example.txt

Permissions

The chmod command changes the permissions and attributes for a file.

To change the permissions for example.txt to read for write for owner, read for group and no acces for any other users:

sudo chmod 640 example.txt

To make a file called example.sh executable:

chmod +x example.sh


Filter command output

grep

You can use grep to filter the output from commands.

For example, if you are using the ls command look for a .txt file in a large folder:

ls | grep .txt

Another example, get the process ID for any python scripts running on the system:

ps aux | grep python

Note that grep will always display an entry your actual grep request in the results.

head and tail

You can use the head and tail command to see the first or last line of text in a file.

To see the first five lines in a file called example.txt:

head -5 example.txt

To see the last ten lines in a file called example.txt:

tail -10 example.txt


Running processes

To view all running processes and their PIDs:

ps aux

To view an active list of running processes:

top

To kill a running process with a PID of 2575:

sudo kill 2575



Common Program Commands and Locations

Samba

Samba is a program that shares files and folders with Windows networks

To install Samba:

sudo apt-get install samba-common-bin

Main config file:

/etc/samba/smb.conf

To add user to Samba:

sudo smbpasswd -a username

Starting and Stopping

To start Samba server:

sudo /etc/init.d/samba start

To stop Samba server:

sudo /etc/init.d/samba stop

To restart Samba server:

sudo /etc/init.d/samba restart



Apache2 web server

To install Apache2:

sudo apt-get install apache2

Locations

Main config file: /etc/apache2/apache2.conf

Default document root: /var/www

Log files: /var/log/apache2

Starting and stopping

sudo /etc/init.d/apache2 start

sudo /etc/init.d/apache2 stop

sudo /etc/init.d/apache2 restart



SSH

SSH is a way to access a remote computer from the terminal. it is commonly used to administer servers.

Commands

To install SSH server:

sudo apt-get install openssh-server

To install SSH client:

sudo apt-get install openssh-server

To connect to the remote computer: ssh username@computername or ssh username@IP address

To stop the SSH server:

sudo /etc/init.d/ssh stop

To start the SSH server:

sudo /etc/init.d/ssh start

To restart the SSH server:

sudo /etc/init.d/ssh restart

Locations

The configuration file is in /etc/ssh/sshd_config

Cheers

Anth



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