Unable to locate package software-properties-common

On my Ubuntu 15.04 (I got it as a virtual server), I want to install Unity. I'm going step by step, so first I tried to install software-properties-common, but I got:

$ sudo apt-get install software-properties-common
Reading package lists... Done
Building dependency tree... Done
E: Unable to locate package software-properties-common

Here is the output of cat /etc/apt/sources.list:

deb vivid main restricted universe
deb vivid-updates main restricted universe
deb vivid-security main restricted universe multiverse
deb vivid partner

And here is the output of sudo apt-get update:

Get:1 vivid-security InRelease [64.4 kB]
Get:2 vivid InRelease [218 kB]
Get:3 vivid InRelease [10.3 kB]
Get:4 vivid/partner amd64 Packages [2978 B]
Get:5 vivid-security/main amd64 Packages [166 kB]
Ign vivid/partner Translation-en
Get:6 vivid-security/restricted amd64 Packages [11.2 kB]
Get:7 vivid-updates InRelease [64.4 kB]
Get:8 vivid-security/universe amd64 Packages [66.3 kB]
Get:9 vivid/main amd64 Packages [1364 kB]
Get:10 vivid-security/multiverse amd64 Packages [6045 B]
Get:11 vivid-security/main Translation-en [79.8 kB]
Get:12 vivid-security/multiverse Translation-en [2743 B]
Get:13 vivid-security/restricted Translation-en [2774 B]
Get:14 vivid-security/universe Translation-en [41.2 kB]
Get:15 vivid/restricted amd64 Packages [15.4 kB]
Get:16 vivid/universe amd64 Packages [6485 kB]
Get:17 vivid/main Translation-en [793 kB]
Get:18 vivid/restricted Translation-en [4228 B]
Get:19 vivid/universe Translation-en [4456 kB]
Get:20 vivid-updates/main amd64 Packages [260 kB]
Get:21 vivid-updates/restricted amd64 Packages [13.6 kB]
Get:22 vivid-updates/universe amd64 Packages [127 kB]
Get:23 vivid-updates/main Translation-en [125 kB]
Get:24 vivid-updates/restricted Translation-en [3112 B]
Get:25 vivid-updates/universe Translation-en [74.6 kB]
Fetched 14.5 MB in 28s (506 kB/s)
Reading package lists... Done

Can someone help on how to continue?

1 Answer

After sudo apt-get update, I was able to install software-properties-common.