Config Server

Common commands for Debian Flavors (Ubuntu)

Brief

• If there is a $ symbol, it means it's a terminal command, otherwise it's likely just a path.
• I am excluding the $ sudo command, because it's too repetitive, just $ sudo su to save time.

Enable PPA Repositories

$ apt-get install python-software-properties

Config SSH Settings

$ vim /etc/ssh/sshd_config
$ service ssh restart

Users

See Settings

$ useradd

See the Defaults (Change in /etc/default/useradd)

$ useradd -D

Add a user with the defaults

$ useradd samson

Add user with defaults and home directory

$ useradd -m samson

Add user with bash as shell if not set

$ useradd -m -s /bin/bash jesse

Change user password

$ passwd samson

Delete User

$ userdel samson

See Users

$ cat /etc/passwd

See Groups

$ cat /etc/group

Add to sudo (Super User) You have to re-login for sudo to take effect

$ adduser samson sudo

Manually Add sudo (Super User)

/etc/sudoers has: %sudo   ALL=(ALL:ALL) ALL
$ visudo

You could also add per user, rather than include per group within /etc/sudoers

samson ALL=(ALL) ALL

Change a users shell

sudo chsh -s /bin/bash samson

Add Existing user to Existing Group

usermod -a -G www-data samson

User Keys

Use an existing SSH key. Paste your id_rsa.pub in one line in the file:

mkdir ~/.ssh
vim ~/.ssh/authorized_keys

Use the same key to authorize Git

touch ~/.ssh/id_rsa.pub

Or, create a new SSH key

ssh-keygen -t -rsa -C "email@gmail.com"

SSH Directory Permissions

~/.ssh              700
~/.ssh/id_rsa.pub   644
~/.ssh/id_rsa       600

One liner permissions

chmod 700 ~/.ssh && chmod 644 ~/.ssh/id_rsa.pub

If you have a Private Key also

chmod 700 ~/.ssh && chmod 644 ~/.ssh/id_rsa.pub && chmod 600 ~/.ssh/id_rsa

IP Tables

/etc/init.d/iptables has been removed a while ago, so managing them is different for old schoolers.

Easy to manage persistent IP-Tables

$ apt-get install iptables-persistent

Using persistant iptables:

$ /etc/init.d/iptables-persistent

This will save the rules for IPv4/v6 in: /etc/iptables/, Also refer to IP Tables Wiki for startup.

List out IP Table Rules

$ sudo iptables -L

List IP Tables with the Line Number

$ sudo iptables -vnL –line-numbers

Add an INPUT rule (Change the port)

$ sudo iptables -A INPUT -p tcp --dport 9898 -j ACCEPT

Delete a IP Table Rule (Get the list from above)

$ iptables -D INPUT <list-number>

Permanently save IP Table Rules if satisfied with $ sudo iptables -L From there, if you are not using iptables-persistent you would want a bash script to load in /etc/init.d/ or the /etc/network/ip-up.d.

$ touch /ectc/firewall.conf
$ iptables-save > /etc/firewall.conf

Manage Network Scripts

/etc/network/if-down.d/
/etc/network/if-pre-up.d/

Make sure to chmod +x filename.sh

www folder user/group permissions

To best share with multiple users who should be able to write in /var/www, it should be assigned a common group. For example the default group for web content on Ubuntu and Debian is www-data. Make sure all the users who need write access to /var/www are in this group. Source

$ usermod -a -G www-data <some_user>

Then set the correct permissions on /var/www.

$ chown -R www-data:www-data /var/www 
$ chmod -R g+w /var/www
# Relogin for changes to apply

Additionally, you should make the directory and all directories below it "set GID", so that all new files and directories created under /var/www are owned by the www-data group.

$ find /var/www -type d -exec chmod 2775 {} \;

Find all files in /var/www and add read and write permission for owner and group:

$ find /var/www -type f -exec chmod ug+rw {} \;

Using Networking

Beginner commands to http://www.linux.com/learn/tutorials/290879-beginners-guide-to-nmap

$ apt-get install nmap

Check open ports

$ sudo nmap -sT -O localhost

Other ways to check ports

$ netstat -anp | grep 222
$ lsof -i | grep 222
$ telnet localhost 222