Unable to update once apt-offline has sync'd packages

[virgilc73]

Greetings!
First, thankyou for your work on the apt-offline project. I am trying to use it to update Ubuntu 18.04 on some air-gapped machines and am having some issues getting it to work. The following were my steps:

1. Installed apt-offline on both on-line and off-line test machine.
   a. apt-offline (version 1.8.1 all) installed to on-line machine using apt repository
   b. apt offline (version 1.8.1 all) and dependencies installed using dpkg -i
2. Created signature on offline machine for updates: sudo apt-offline set --update apt-offline_update.sig
3. Transferred the signature to online machine and grabbed repo update: sudo apt-offline get --bundle update.zip apt-offline_update.sig
4. Copied update.zip to offline machine and ran: sudo apt-offline install update.zip
   a. Select Y to proceed with installation
   b. Got ERROR: Path for keyring is invalid: /etc/apt/trusted.gpg
   i. I did not see this as an issue as all the the needed gpg files were in /etc/apt/trusted.gpg.d/
   c. Looks like all the packages synced successfully
5. Created signature on offline machine for upgrades: sudo apt-offline set --update --upgrade apt-offline_upgrade.sig
6. Transferred the signature to online machine to get upgrades: sudo apt-offline get --bundle upgrade.zip apt-offline_upgrade.sig
7. Copied upgrade.zip to offline machine and ran: sudo apt-offline install upgrade.zip
   a. results were exactly the same as update process (I was expecting the bundles to be different sizes, but they were both 37.6MB)
8. Once completed I ran apt upgrade and it looked normal, displaying the following:
   Reading package lists...Done
   Building dependency tree
   Reading stat information... Done
   Calculating upgrade... Done
   The following packages will be upgraded:
   Lotsa packages listed
   155 upgraded, 0 newly installed 0 to remove and 0 not upgraded
   137 standard security updates
   need to get 205 MB of archives.
   After this operation, 1,716 kB of additional disk space will be used.
   Do you want to continue? [Y/n] Y
   9 I am now seeing the following errors for all of the packages:
   Ign:1 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 bash amd64 4.4.18-2ubuntu1.3
   Err:2 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 libc6 amd64 2.27-3ubuntu1.6
   Temporary failure resolving 'archive.ubuntu.com'
   Err:1 http://security.ubuntu.com/ubuntu bionic-updates/main amd64 bash amd64 4.4.18-2ubuntu1.3
   Temporary failure resolving 'archive.ubuntu.com'
   Ign:3 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 cron amd64 3.0pl1-128.1ubuntu1.2
   Ign:4 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 tar amd64 1.29b-2ubuntu0.3
   Err:3 http://security.ubuntu.com/ubuntu bionic-updates/main amd64 cron amd64 3.0pl1-128.1ubuntu1.2
   Temporary failure resolving 'archive.ubuntu.com'
   .....
9. At the end of this process nothing is upgraded.

Based on this information is there anything you can suggest? I have read the wiki and watched the youtube video, but this is still not working for me.

I also checked /var/cache/apt/archives and found that it does not contain any packages. Is that were apt-offline is supposed to extract the packages?

[rickysarraf]

I know it is quite late in asking this but better ask than keep mum.

For Step 3, can you please share more details ? Like console output etc.