The PASS_MIN_DAYS parameter in /etc/login.defs allows an administrator to prevent users from changing their password until a minimum number of days have passed since the last time the user changed their password. It is recommended that PASS_MIN_DAYS parameter be set to 7 or more days. Rationale: By restricting the frequency of password changes, an administrator can prevent users from repeatedly changing their password in an attempt to circumvent password reuse controls.

[7 days]

Set the PASS_MIN_DAYS parameter to 7 in /etc/login.defs: PASS_MIN_DAYS 7 Modify active user parameters to match: # chage -mindays 7 <user>