Install ruby2.2.3 with RVM on ubuntu 21.04 [duplicate]

Solution 1:

Execute the following commands in terminal

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys <PUBKEY>

where <PUBKEY> is your missing public key for repository, e.g. 8BAF9A6F.

Then update

sudo apt-get update

ALTERNATE METHOD:

sudo gpg --keyserver pgpkeys.mit.edu --recv-key  <PUBKEY>
sudo gpg -a --export <PUBKEY> | sudo apt-key add -
sudo apt-get update

Note that when you import a key like this using apt-key you are telling the system that you trust the key you're importing to sign software your system will be using. Do not do this unless you're sure the key is really the key of the package distributor.

Solution 2:

By far the simplest way to handle this now is with Y-PPA-Manager (which now integrates the launchpad-getkeys script with a graphical interface).

To install it, first add the webupd8 repository for this program:
```
sudo add-apt-repository ppa:webupd8team/y-ppa-manager
```

Update your software list and install Y-PPA-Manager:

sudo apt-get update
sudo apt-get install y-ppa-manager

Run y-ppa-manager (i.e. type y-ppa-manager then press enter key).
When the main y-ppa-manager window appears, click on "Advanced."
From the list of advanced tasks, select "Try to import all missing GPG keys" and click OK.

You're done! As the warning dialog says when you start the operation, it may take quite a while (about 2 minutes for me) depending on how many PPA's you have and the speed of your connection.

Solution 3:

It happens when you don't have a suitable public key for a repository.

To solve this problem use this command:

gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv 9BDB3D89CE49EC21

which retrieves the key from ubuntu key server. And then this:

gpg --export --armor 9BDB3D89CE49EC21 | sudo apt-key add -

which adds the key to apt trusted keys.

The solution can be found here & here & here.

Solution 4:

You need to get and import the key.

To get the key from a PPA, visit the PPA's Launchpad page. On every PPA page at Launchpad you will find this link (2), after clicking on 'Technical details about this PPA' (1):

Follow it and click on the key ID link (3):

Save the page, this is your key file.

Now it's time to import it:

Applications > Software Center,
Edit > Software sources...,
Enter your password,
Go to the Authentication tab and click on Import Key File..., finally
Select the saved key file and click on OK.

Solution 5:

apt can only handle 40 keys in /etc/apt/trusted.gpg.d . 41 keys and you will get the GPG error "no public key found" even if you go through all the steps to add the missing key(s).

Check to see if there are any unused keys in this file from ppa(s) you no longer use. If all are in use, consider removing some ppa(s) along with the corresponding keyfiles in /etc/apt/trusted.gpg.d

Furthermore, using

sudo apt-key adv

Is considered a security risk and is not recommended as you are "undermining the whole security concept as this is not a secure way of recieving keys for various reasons (like: hkp is a plaintext protocol, short and even long keyids can be forged, …)". http://ubuntuforums.org/showthread.php?t=2195579

I believe the correct way to add missing keys (for example 1ABC2D34EF56GH78) is

gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv 1ABC2D34EF56GH78
gpg --export --armor 1ABC2D34EF56GH78 | sudo apt-key add -