E: Package 'apache2' has no installation candidate on Ubuntu 17.10

Solution 1:

The main problem is missed /etc/apt/sources.list. You can recreate it with:

cat <<EOF | sudo tee /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu $(lsb_release -cs) main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu $(lsb_release -cs)-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu $(lsb_release -cs)-security main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu $(lsb_release -cs)-backports main universe restricted multiverse
EOF

Then run

sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install apache2

Solution 2:

Try sudo apt-get update and then sudo apt-get install apache2. I recommend installing the complete LAMP Stack using tasksel

sudo apt-get install tasksel

sudo tasksel to launch it Select LAMP server and install it. Hope that helps.