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I am trying to install Darktable on my Ubuntu 12.04 64bit desktop computer. When I attempt to install it through the Ubuntu Software Centre I get a warning:

"Requires installation of untrusted packages"

The "Details" are: darktable libflickcurl0 liblensfun-data liblensfun0

There are two options, OK and Repair. If I choose Repair, it fails to "download repository information".

If I try to add the PPA via terminal and install it, I get cryptic messages about not being able to verify the gpgkey.

Does this mean it is unsafe to install? I would really like to get this running (safely) as I am a professional photographer and I want to share my workflow with the Linux community.


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On a side note, can you post the error message you get when trying to get the GPG key? I can update my answer to be more complete. Hopefully I can give you some commands to actually fix the issue rather than ignoring it. –  Githlar Oct 12 '12 at 1:51

2 Answers 2

It turns out it was a network problem, which explains the 407 Proxy Authentication errors.

From System Settings I went to Network. I clicked on my proxy connection, selected Configure, and noticed the proxy was set to "Connect Automatically". I disabled the automatic proxy connection and was able to update and install software again without problems.

Thanks for all your help.

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The reason you're getting this "untrusted" error is because of the GPG key download failure. Modern repositories are signed with a private GPG key and they distribute a public GPG key so that the signature can be verified by end-users.

Theoretically this helps to prevent package downloads in the case that somebody replaces a package on the repository site with an unsigned version (may contain malware, spyware, etc.) This assumes that the "attacker" doesn't have the private GPG key to sign the packages.

So, you're getting the error because of the failed GPG key download. Apt can't verify the integrity of the package signature because it doesn't have the public key available to decrypt it.

Generally, it's not a good idea to download/install unverified software. But if you know the software and trust it, you can go ahead and install it without worries.

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Thank you. I've been worried to install it because of this. So do the software maintainers need to update their public GPG key or something. Or is there a problem on my end downloading it? –  Devi710 Oct 12 '12 at 1:53
I don't know, you didn't post the output ;) –  Githlar Oct 12 '12 at 1:55
Oh sorry. Good point ;) It's long, I'll try and fit it in the next comment. And thanks for all your help. –  Devi710 Oct 12 '12 at 1:59
W:Failed to fetch extras.ubuntu.com/ubuntu/dists/precise/main/source/Sources 407 Proxy Authentication Required , W:Failed to fetch dl.google.com/linux/chrome/deb/dists/stable/main/binary-amd64/… 407 Proxy Authentication Required , W:Failed to fetch security.ubuntu.com/ubuntu/dists/precise-security/main/source/… 407 Proxy Authentication Required , W:Failed to fetch archive.getdeb.net/ubuntu/dists/precise-getdeb/games/… 407 Proxy Authentication Required –  Devi710 Oct 12 '12 at 2:01
It keeps going like that for another 9000 characters and ends with: W:Failed to fetch ca.archive.ubuntu.com/ubuntu/dists/precise-backports/restricted/… 407 Proxy Authentication Required , W:Failed to fetch ca.archive.ubuntu.com/ubuntu/dists/precise-backports/universe/… 407 Proxy Authentication Required , W:Failed to fetch ca.archive.ubuntu.com/ubuntu/dists/precise-backports/multiverse/… 407 Proxy Authentication Required , E:Some index files failed to download. They have been ignored, or old ones used instead. –  Devi710 Oct 12 '12 at 2:02

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