Linux Command Directory

Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

Buy it now, or read it online on Safari Bookshelf.


pwck [options] [files]

System administration command. Remove corrupt or duplicate entries in the /etc/passwd and /etc/shadow files. pwck will prompt for a "yes" or "no" before deleting entries. If the user replies "no," the program will exit. Alternate passwd and shadow files can be checked. If correctable errors are found, the user will be encouraged to run the usermod command.



Run in quiet mode. Only report serious problems.


Run in noninteractive read-only mode, answering all questions no.


Don't check integrity, just sort entries by UID.

Exit status




Syntax error.


One or more bad password entries found.


Could not open password files.


Could not lock password files.


Could not write password files.

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