Ubuntu Doc page says this:

It is advisable that you add the Opera GPG key.

wget -qO - | sudo apt-key add -

Where do I add that?

I want to take the advice but I don't know what part of software center to add gpg keys to.

4

6 Answers

This a a one line command to enter in terminal. SeeWhat is a terminal and how do I open and use it?

To use it, you would paste the entire command in the terminal (remember to use https):

wget -qO - | sudo apt-key add -

But of course, it is daunting just copying and pasting commands without knowing what they are doing, and having no instructions on how to undo their actions, so here is a basic breakdown of the commands:

• wget downloads something from a server. See wget manual for Ubuntu 16.04.
• | is a pipline, which takes the output of one command and runs it into the input of another
• apt-key add adds a package key

So it basically downloads the key and then adds it in one command.

I tested the command and it should work.

---

Now to verify that it worked, run this command (from this answer):

apt-key list

This will list the keys added and the key from Opera should be listed on the bottom like this:

pub 1024D/30C18A2B 2012-10-29 [expires: 2014-10-29]
uid Opera Software Archive Automatic Signing Key 2013 <>
sub 4096g/C528FCA9 2012-10-29 [expires: 2014-10-29]

The linked answer also shows that you can remove the key if needed, using:

sudo apt-key del 30C18A2B

with 30C18A2B being the key-id from the list.

---

After performing that command, and setting up the sources exactly like in your screen-shot, do:

sudo apt-get update
sudo apt-get install opera

(note there are some random warnings, but nothing that affects the install or software center operations)

And for the removal (just in case): What is the correct way to completely remove an application?

---

So in summary:

• Add repository
• Add key with apt-key
• Install in terminal with apt-get
• Search in dash

4

If you are manually adding a key from a PPA, use

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 00000000

Replacing the 00000000 with the second part of the key informed in the PPA website that you want to add.

For example, if you find this line:

 4096R/7BF576066

Use only the second part (no matter its size), which in this example is 7BF576066

2

Newer versions of apt also support the following:

apt-key adv --fetch-keys 

This method also provides more detailed feedback as well, e.g.:

gpg: key 7BD9BF62: public key "signing key <>" imported
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)

This also has the added bonus of removing the need for additional dependencies like wget or curl.

4

You should not add third-party keys via apt-key add. These keys can then be used to sign any package on your machine, including those from the archive. Now you should only allow the key to sign only a specific package. Complete answer on UNIX.SE from user Trudy.

apt-key now seems to be deprecated, I have created a script that will detect and get the missing keys, you can get it here.

#!/bin/sh -e
tmp="$(mktemp)"
sudo apt-get update 2>&1 | sed -En 's/.*NO_PUBKEY ([[:xdigit:]]+).*/\1/p' | sort -u > "${tmp}"
cat "${tmp}" | xargs sudo gpg --keyserver "hkps://keyserver.ubuntu.com:443" --recv-keys # to /usr/share/keyrings/*
cat "${tmp}" | xargs -L 1 sh -c 'sudo gpg --yes --output "/etc/apt/trusted.gpg.d/$1.gpg" --export "$1"' sh # to /etc/apt/trusted.gpg.d/*
rm "${tmp}"

Another way where you just have an .asc key, you download the .asc key and add it to the keyring.

For instance -

curl -L | sudo apt-key add -

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