grpck

Verify the integrity of group files.

Supplemental Information

The grpck command is used to verify the integrity of group files. Before verification, the group files /etc/group and /etc/gshadow are locked.

grpck checks if the data is correctly stored, if each record contains sufficient information, if there is a unique group name, if it contains valid users, and if group administrators are correctly set. If grpck detects an error, it prompts the user to delete the erroneous record. If the user does not explicitly choose to delete the record, grpck terminates.

Syntax

grpck (options)

Options

-r: Read-only mode;
-s: Sort entries by group ID.

Examples

Verify the group and shadow files:

grpck   # Must be run as root
grpck /etc/group /etc/gshadow   # The two forms are equivalent; no output indicates no errors.

Example of testing an error:

# Add an incorrectly formatted line
echo check_user:x: >> /etc/group
cat /etc/group | grep check_user
# check_user:x:  (The GID field is empty, which is an error.)

grpck /etc/group 
# invalid group file entry
# delete line 'check_user:x:'? y      # Prompt to delete
# grpck: the files have been updated  # The erroneous line has been deleted.

cat /etc/group | grep check_user   # No result found, it has been deleted.