A machine may not always be on the same network as the IdM domain; for example, a machine may need to be logged into a VPN before it can access the IdM domain. If a user logs into a system when it is offline and then later attempts to connect to IdM services, then the user is blocked because there is no IdM Kerberos ticket for that user. IdM works around that limitation by using SSSD to store the Kerberos passwords in the SSSD cache.

This is configured by default by the ipa-client-install script. A configuration parameter is added to the /etc/sssd/sssd.conf file which specifically instructs SSSD to store those Kerberos passwords for the IdM domain:

[domain/example.com]
cache_credentials = True
ipa_domain = example.com
id_provider = ipa
auth_provider = ipa
access_provider = ipa
chpass_provider = ipa
ipa_server = _srv_, server.example.com
krb5_store_password_if_offline = true

This default behavior can be disabled during the client installation by using the --no-krb5-offline-passwords option.

This behavior can also be disabled by editing the /etc/sssd/sssd.conf file and removing the krb5_store_password_if_offline line or changing its value to false.

[domain/example.com]
...
krb5_store_password_if_offline = false

The SSSD configuration options for Kerberos authentication is covered in the "Configuring Domains" section of the SSSD chapter in the Red Hat Enterprise Linux Deployment Guide.