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Linux: Embedded Development by Chris Simmonds, Alex González, Alexandru Vaduva

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Managing users and groups

It is also common to need to add or modify users and groups to our filesystem. This recipe explains how it is done.

Getting ready

The user information is stored in the /etc/passwd file, a text file that is used as a database for the system user's information. The passwd file is human-readable.

Each line on it corresponds to one user in the system, and it has the following format:

<username>:<password>:<uid>:<gid>:<comment>:<home directory>:<login shell>

Let's see each of the parameters of this format:

  • username: A unique string that identifies the user at login
  • uid: User ID, a number that Linux uses to identify the user
  • gid: Group ID, a number that Linux uses to identify the user's primary group
  • comment: Comma-separated values ...

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