ktutil

ktutil is a command-line utility used to edit Kerberos keytab files. It is part of Kerberos distributions such as MIT Kerberos and Heimdal and is employed to create, inspect, and modify keytab entries. A keytab stores secret keys for Kerberos principals so that services can authenticate without interactive passwords.

Keytab files are used by services to obtain the keys needed for Kerberos authentication. ktutil provides an interactive environment with commands to list entries, add new entries, delete entries, and read from or write to keytab files. This makes it a practical tool for administrators who need to build or update keytabs used by daemon processes and services.

Typical workflows involve creating or updating a service’s keytab. Administrators may use ktutil in conjunction with other Kerberos tooling to populate a keytab with the appropriate keys for a given service principal, and then deploy the keytab to the host where the service runs. The keytab is then used by the service at startup or when renewing credentials.

Each keytab entry contains a principal name (such as a service/host and realm), an encryption type (etype), a key version number (kvno), and the key material. The keytab file is typically binary and not meant to be human-readable; its content must be protected and access restricted to trusted administrators.

Security considerations include limiting access to keytab files, rotating keys as part of regular security practice, and auditing changes to keytabs. See Kerberos, kadmin, and keytab for related concepts.