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Hands-on Lab·Linux Foundation Certified System Administrator

Groups and shared directories

Group membership is examined constantly, and the mistake that costs marks is one missing letter: usermod -G replaces the supplementary group list while -aG adds to it. This guide shows the difference on a live account, then builds the shared directory that group membership exists for.

Users and Groups Guide 19 of 38 Intermediate

shadow-utils, identical on both families. The admin group is wheel on RHEL and sudo on Debian and Ubuntu - the same idea with a different name.

Both families. The RHEL transcript came first, during an outage that took both Ubuntu hosts offline; the Ubuntu half was captured afterwards and is the last step of each page, because Ubuntu is what LFCS is most likely to sit you in front of.
Server NameIP AddressOSRolesCPURAMHDD
LFCS-A01192.168.0.70Ubuntu 26.04 LTSPrimary host - most guides run only here2 Core4 GB50 GB
LFCS-C01192.168.0.72AlmaLinux 10.2The other distribution - dnf, firewalld and NetworkManager2 Core4 GB50 GB

This guide includes

Use this because group membership is examined constantly. This matters because usermod -G replaces the supplementary groups rather than adding to them - quietly removing access somebody already had.

Before you start

  1. Primary and supplementary

  2. The flag that replaces instead of adding

  3. Changing the primary group

  4. The shared directory groups exist for

  5. The same commands on Ubuntu

Official sources

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