command sudo usermod -aG <newgroup> <user> behaves like usermod -G in shadow-utils 4.8.1

[mgw2013]

I'm afraid, this looks like a bug...

command sudo usermod -aG <newgroup> <user> behaves like usermod -G in shadow-utils 4.8.1 i. e. all group access for <user> is removed and only <newgroup> is added.

Among others the result was I threw myself out of the sudo group and had to restore everything manually with a life stick...

System:
michael@W520 ~ $ inxi -Sz System: Kernel: 5.15.0-91-generic x86_64 bits: 64 Desktop: Cinnamon 5.8.4 Distro: Linux Mint 21.2 Victoria
man and info reporting shadow-utils 4.8.1 11/24/2022

[alejandro-colomar]

You mean that the bug was introduced in (or slightly before) 4.8.1?
Do you have other shadow versions available? Did you upgrade recently?

[mgw2013]

@alejandro-colomar
Unable to answer ur 1st question.
No shadow versions.
The system is on latest release and is fully updated
System: Kernel: 5.15.0-91-generic x86_64 bits: 64 Desktop: Cinnamon 5.8.4 Distro: Linux Mint 21.2 Victoria