This page is for the things I learn on my Linux travels. Mainly this (at the time of writing) due to several Linux based products in my workplace (CentOS based) and the truly amazing Raspberry Pi range. I have not yet decided whether to split the Linux page in to two sub categories to reflect this.

Configure Static IP Address

Raspbian Jesse changed the way a static IP Address is configured. The static IP settings are now held in a file located in the /etc directory called dhcpcd.conf

To edit the dhcpcd.conf file, enter:
sudo /etc/dhcpcd.conf

At the end of the file add the following lines (with your own IP Address values)

eth0
static ip_address=192.168.1.14/24
static routers=192.168.1.1
static domain_name_servers=192.168.1.4

Save and reboot.

Here are a few useful MySQL commands you can run from the command line, handy if you have installed MySQL and you don't have desktop access or a graphical MySQL manager application.

Login to MySQL First we must login
mysql -u root -p — (the root part assumes root is your mysql username)

Create a MySQL Database
CREATE DATABASE new_database; — (don't forget the semicolon ; it's really important)

Show a MySQL Database
SHOW DATABASES;

Uncomplicated Firewall UFW is a much simpler security solution than using iptables, it is very easy to install and configure. iptables might ultimately have more features, but I think UFW is suitable for most users.

To install UFW from the command line:
sudo apt-get install ufw

To allow all ports on the local subnet:
sudo ufw allow from 192.168.0.0/24 (allow access from 192.168.0.1 - 192.168.0.254)

Allow web port 80 to everyone (internal and external LAN)
sudo ufw allow 80

To enable UFW and start rules:
sudo ufw –force enable

From time to time it might be necessary to restart the Apache Web Server, normally this is required after a configuration change, or if a site has stopped.

From the command line:
sudo /etc/init.d/apache2 restart

Working from the command line has some disadvantages, one of those is that you don't have a constant graphical reminder of physical and available disk space. To check this we can use the command df which stands for disk filesystem

From the command line:
df -h — (the -h means human readable format, so instead values being in bytes, they are displayed at MB or GB etc)

$ df -h

Filesystem Size Used Avail Use% Mounted on
/dev/root 6.0G 3.7G 2.0G 66% /
devtmpfs 214M 0 214M 0% /dev
tmpfs 218M 0 218M 0% /dev/shm
tmpfs 218M 4.5M 213M 3% /run
tmpfs 5.0M 4.0K 5.0M 1% /run/lock
tmpfs 218M 0 218M 0% /sys/fs/cgroup
/dev/mmcblk0p6 63M 20M 43M 32% /boot
tmpfs 44M 0 44M 0% /run/user/1000

To change the password for a user, when logged in as that user, from the command line enter:

sudo passwd pi — (make sure you use the correct username, pi is just for the example)
you will then be prompted to enter, then re-enter the new password

$ sudo passwd pi
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully