Apt update failed because public key not available
6809
How do I fix the GPG error "NO_PUBKEY"?
60835
dpkg: error: failed to open package info file `/var/lib/dpkg/available' for reading
56150
Can't upgrade/update ubuntu 18.04 as apt/dpkg error is showing up
126437
pass and gpg: No public key
27769
Problem with IPv6 sudo apt-get update/upgrade
30754
Cannot update: "No available releases found"
64509
Can't update from official repositories [Error 409]
12368
A "failed to fetch" error occurs when apt-get update is run. How do I fix this?
41519
What can I do if a package is not available on the newest version of Ubuntu (18.04) but is available on older versions?
3523
What does "Package  has no installation candidate" mean?
728
Unable to lock the administration directory (/var/lib/dpkg/) is another process using it?
1632
How do I fix a "Failed to download package files" error?
48418
W: GPG error: http://ppa.launchpad.net precise Release: The following signatures couldn't be verified because the public key is not available:
117728
sudo apt update error
5565
How to fix Permission Denied (Public key) error?
43579
I cannot install new packages: "Could not get lock /var/lib/dpkg/lock"
11909
404 error with apt-get update, Don't have any PPA's