pwck, chage, and passwd commands

The pwck command is a Linux system administration tool that is used to verify the consistency of the passwd, shadow, and group files. The purpose of the command is to ensure that the user accounts and groups listed in these files are valid and to detect any inconsistencies between them. It is useful in maintaining the integrity and security of a Linux system, as it can help to identify and correct errors that may arise due to manual edits of these files. For example, if a user account exists in the passwd file but not in the shadow file, pwck will detect this and prompt the user to fix the inconsistency. Let’s take a look at some examples using this tool:

• Verify the consistency of the passwd file with sudo pwck /etc/passwd.

  The following output from the pwck command checks the consistency of the /etc/passwd file on our Linux system:

Figure 2.22 – Checking the consistency of the /etc/passwd file

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