Updated Date: 07/07/2026
The f5mku utility: Reference
The f5mku utility is a cryptographic tool for managing passwords and passphrases. The available command options that display when you type f5mku -h at a system prompt are listed below.
Important: F5 recommends not using the f5mku utility on a BIG-IQ system.
Warning: F5 strongly recommends that you avoid using the -r option to reset a master key. Using -r without first decrypting the passwords or passphrases on configuration objects will cause any subsequent configuration load operation to fail. Use the TMOS Shell (tmsh) command modify /sys master-key prompt-for-passwordinstead.
[a2w@COSFL02:/S1-green-P:Active:Disconnected] ~ # f5mku -h
Usage: f5mku [d:?fhHi:r:t:uUvYZq:]
Required parameters: (one of these must be specified)
-d bits generate a base64 encoded RSA key and output to stdout
-f fetch unit key
-Z dump debug information
-i file import key saved via ---
-r key rekey with the specifed master key (b64 encoded). Use with caution.
Optional parameters:
-? -h this help
-q Query if given string matches current master key
-t # Timeout value in seconds (1-500)
-u Unit test posture (no HAL)
-U Test unit key functionality
-H Force I/O to HAL storage
-K Displays the master key
-v set verbose mode
-Y Answer Yes to any queries