Unless you've installed REMnux in the addon mode, the distro disabled automated Ubuntu update mechanisms for the OS. This allows you to control how and when your REMnux system attempts to initiate network connections, and avoids issues when REMnux on an isolated network.
Keep your REMnux system up to date by running the following command once in a while, so you benefit from the latest enhancements. Be sure to first connect the system to the internet.
remnux upgrade
Even if if the command above tells you, "No upgrades available," you can still refresh your current tools. The following operation will make sure that you're running the latest versions of the installed Debian packages and Python modules, without adding adding any new tools to your system:
remnux update
To sum up, the upgrade option updates all the tools and adds new ones that might have been incorporated into the REMnux distro. The update command is a subset, and updates your existing Debian packages and Python modules.
If you're running the REMnux distro in a virtual machine, consider taking a snapshot before upgrading or updating your VM, so you can revert to a good state if something goes wrong.
If you receive an error upgrading or updating the REMnux distro when using the remnux command, refresh your APT package database by issuing the following commands, then trying the operation again:
sudo apt updatesudo apt autoremovesudo apt --fix-broken install
If the issue persists, diagnose the problem by reviewing the saltstack.log file under /var/cache/remnux/cli in the subdirectory that matches the REMnux state-files version you're installing. Search for the log file for result: false messages and look at the surrounding 5 lines or the 8 lines above each message to see the state file that caused the issue. (grep -i -C 5 'result: false' or grep -i -B 8 'result: false').