How do I specify the number of days between which users should change their password in Linux?

[petulia3478]

To make users change their password after 30 days:

# /usr/bin/chage -m 30 testuser

You can check the result in /etc/shadow:

# /bin/grep testuser /etc/shadow
testuser:$1$wypNKIu9$Ib3YmLexp7BVl88crX5eE/:14445:30:99999:2::14446: