Who, and with Whom?

Charly's Column – User Groups

Article from Issue 248/2021
Author(s):

This time Charly investigates the three most frequently asked questions about user groups.

Most people know that every user on a Linux system is also a member of at least one user group. Today we want to look into the three most frequently asked questions about groups: Which groups exist, how many members does a group have and who are those members, and to what groups does a specific user belong?

First off, let's find out which groups exist on our system. There are several ways to do this. One of them is to use the groups command without further parameters; another one is provided by compgen -g. The getent group (Listing 1, line 1) and cat /etc/group commands also return the same result, with some additional information, including the group password. There is usually an x here, which means that /etc/gshadow takes care of that. This is followed by the numeric group ID and a comma-separated list of members.

The next thing is to find out which members belong to a group. In principle, we have already done this, because the getent group and cat /etc/group commands provide this information as well.

[...]

Use Express-Checkout link below to read the full article (PDF).

Buy this article as PDF

Express-Checkout as PDF
Price $2.95
(incl. VAT)

Buy Linux Magazine

SINGLE ISSUES
 
SUBSCRIPTIONS
 
TABLET & SMARTPHONE APPS
Get it on Google Play

US / Canada

Get it on Google Play

UK / Australia

Related content

  • Charly's Column

    Leafnode is a Usenet server for small sites where just a few users need access to a large number of groups. The Leafnode server is designed to recover from errors autonomously and needs very little attention.

  • Charly’s Column: Cluster SSH

    Charly doesn’t relish the idea of searching through the logfiles of a dozen proxy servers when page requests fail. Now that he has deployed Cluster SSH, he can pull the strings on many machines at the same time.

  • Charly's Column: Terminator

    Friends are all about friendship – names and appearances typically don’t play any role at all. Sys admin Charly’s friend the Terminator is a convincing example.

  • Charly’s Column: w3af

    After toiling away to create a small but exclusive website, Charly wanted to run a security scanner against it to check for vulnerabilities. The choice of tools is enormous, but Charly chose w3af.

  • Charly's Column: Nmon

    Nmon monitors system information. You can use the Nmon’s capture mode to output data to a file, then extract the values you need with a script.

comments powered by Disqus

Direct Download

Read full article as PDF:

Price $2.95

News