A common error in Linux

A very common error in Linux; well, most Debian based Linux distributions such as Debian itself, Ubuntu, Kali, Linux Mint has this error when trying to install a package/application “Package packagename is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source. E: Package ‘packagename’ has no installation candidate”

Package somePackage is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package somePackage has no installation candidate

Extremely annoying and useless error that doesn’t tell you much on how to fix it.

Fixing “Package packagename is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source. E: Package ‘packagename‘ has no installation candidate” error

However, this is rather eacy to fix. Just use the following command in any Debian based Linux Operation system such as Debian itself, Ubuntu, Kali Linux, Linux Mint etc.

sudo apt-get update && && sudo apt-get upgrade -y && sudo apt-get dist-upgrade -y && sudo apt-get install packagename
(or)
apt-get update && apt-get upgrade -y && apt-get dist-upgrade -y && apt-get install packagename

(where packagename refers to the package that failed to install in the first place)

Once you’ve updated, upgraded, you should be able to install any packages without errors.

Download GPG Authentication Key

Assuming you already have GPG (GnuPG) installed (most Linux distro these days have GPG pre-installed), you can download a copy of your Linux distributions official key.

Kali Linux

Use the following commands: (Source: Downloading Kali Linux. Also thanks to user emra for pointing it out, Cheers)

wget -q -O - https://www.kali.org/archive-key.asc | gpg --import

or the command

gpg --keyserver hkp://keys.gnupg.net --recv-key 7D8D0BF6

Your output should look like this:

gpg: key 7D8D0BF6: public key "Kali Linux Repository <devel@kali.org>" imported
gpg: Total number processed: 1
gpg:               imported: 1  (RSA: 1)

Verify that the key is properly installed with the command:

gpg --list-keys --with-fingerprint  7D8D0BF6

The output will look like this:

pub   4096R/7D8D0BF6 2012-03-05 [expires: 2015-03-05]
Key fingerprint = 44C6 513A 8E4F B3D3 0875  F758 ED44 4FF0 7D8D 0BF6
uid       [ unknown] Kali Linux Repository <devel@kali.org>
sub   4096R/FC0D0DCB 2012-03-05 [expires: 2015-03-05]

You’re now set up to validate your Kali Linux download.

Ubuntu Linux

I have since tried this in an Ubuntu installation I had (I forgot to update it for a very long time). Worked fine.

Error Samples:

W: GPG error: http://ppa.launchpad.net jaunty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6D975C4791E7EE5E

W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://ppa.launchpad.net jaunty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 5A9BF3BB4E5E17B5

W: GPG error: http://ppa.launchpad.net jaunty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7FB8BEE0A1F196A8

W: Failed to fetch http://ppa.launchpad.net/chromium-da...jaunty/Release

W: Some index files failed to download, they have been ignored, or old ones used instead.

The fix for this is to re-download the keys using the hexidecimal numbers given in the error . Note that your hexadecimal numbers may be different then mine, so make sure to use the hexadecimals numbers in your error, not mine.

Type this command into the terminal:

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys

And then add the hexadecimal numbers to the command (again, these are my keys from my error. Make sure to use your own):

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 6D975C4791E7EE5E 5A9BF3BB4E5E17B5 7FB8BEE0A1F196A8"

The output should look like this:

gpg: requesting key 437D05B5 from hkp server keyserver.ubuntu.com"

Once GPG keys are imported, I advise to do an update, upgrade, dist upgrade and then install the package you want. Following command will do just that:

sudo apt-get update && && sudo apt-get upgrade -y && sudo apt-get dist-upgrade -y && sudo apt-get install packagename
(or)
apt-get update && apt-get upgrade -y && apt-get dist-upgrade -y && apt-get install packagename

After this, life should be normal again!