Java SE 21 & JDK 21

The ktab Command

Name

ktab - manage the principal names and service keys stored in a local key table

Synopsis

ktab [commands] [options]

[commands] [options]
Lists the keytab name and entries, adds new key entries to the keytab, deletes existing key entries, and displays instructions. See Commands and Options.

Description

The ktab enables the user to manage the principal names and service keys stored in a local key table. Principal and key pairs listed in the keytab enable services running on a host to authenticate themselves to the Key Distribution Center (KDC).

Before configuring a server to use Kerberos, you must set up a keytab on the host running the server. Note that any updates made to the keytab using the ktab tool don't affect the Kerberos database.

A keytab is a host's copy of its own keylist, which is analogous to a user's password. An application server that needs to authenticate itself to the Key Distribution Center (KDC) must have a keytab which contains its own principal and key. If you change the keys in the keytab, you must also make the corresponding changes to the Kerberos database. The ktab tool enables you to list, add, update or delete principal names and key pairs in the key table. None of these operations affect the Kerberos database.

Security Alert

Don't specify your password on the command line. Doing so can be a security risk. For example, an attacker could discover your password while running the UNIX ps command.

Just as it is important for users to protect their passwords, it is equally important for hosts to protect their keytabs. You should always store keytab files on the local disk and make them readable only by root. You should never send a keytab file over a network in the clear.

Commands and Options

-l [-e] [-t]
Lists the keytab name and entries. When -e is specified, the encryption type for each entry is displayed. When -t is specified, the timestamp for each entry is displayed.
-a principal_name [password] [-n kvno] [-s salt | -f] [-append]

Adds new key entries to the keytab for the given principal name with an optional password. If a kvno is specified, new keys' Key Version Numbers equal to the value, otherwise, automatically incrementing the Key Version Numbers. If salt is specified, it will be used instead of the default salt. If -f is specified, the KDC will be contacted to fetch the salt. If -append is specified, new keys are appended to the keytab, otherwise, old keys for the same principal are removed.

No changes are made to the Kerberos database. Don't specify the password on the command line or in a script. This tool will prompt for a password if it isn't specified.

-d principal_name [-f] [-e etype] [kvno | all| old]

Deletes key entries from the keytab for the specified principal. No changes are made to the Kerberos database.

  • If kvno is specified, the tool deletes keys whose Key Version Numbers match kvno. If all is specified, delete all keys.

  • If old is specified, the tool deletes all keys except those with the highest kvno. The default action is all.

  • If etype is specified, the tool only deletes keys of this encryption type. etype should be specified as the numeric value etype defined in RFC 3961, section 8. A prompt to confirm the deletion is displayed unless -f is specified.

When etype is provided, only the entry matching this encryption type is deleted. Otherwise, all entries are deleted.

-help
Displays instructions.

Common Options

This option can be used with the -l, -a or -d commands.

-k keytab name
Specifies the keytab name and path with the FILE: prefix.

Examples