tpm2_getcap - Man Page

Display TPM capabilities in a human readable form.


tpm2_getcap [Options] [CAPABILITY]


tpm2_getcap(1) - Query the TPM for it’s capabilities / properties and print them to the console. It takes a string form of the capability to query as an argument to the tool. Currently supported capability groups are:

TPM2_GetCapability command, and defaults to 1. An example to call it with a property value of 2 is: tpm2_getcap vendor:2

NOTE: if vendor requests hang, try the “-i” option to ignore the moreData field and only read once.


Ignores the moreData field when dealing with buggy TPM responses.

Common Options

This collection of options are common to many programs and provide information that many users may expect.

TCTI Configuration

The TCTI or “Transmission Interface” is the communication mechanism with the TPM. TCTIs can be changed for communication with TPMs across different mediums.

To control the TCTI, the tools respect:

  1. The command line option -T or --tcti
  2. The environment variable: TPM2TOOLS_TCTI.

Note: The command line option always overrides the environment variable.

The current known TCTIs are:

The arguments to either the command line option or the environment variable are in the form:


Specifying an empty string for either the <tcti-name> or <tcti-option-config> results in the default being used for that portion respectively.

TCTI Defaults

When a TCTI is not specified, the default TCTI is searched for using dlopen(3) semantics. The tools will search for tabrmd, device and mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query what TCTI will be chosen as the default by using the -v option to print the version information. The “default-tcti” key-value pair will indicate which of the aforementioned TCTIs is the default.

Custom TCTIs

Any TCTI that implements the dynamic TCTI interface can be loaded. The tools internally use dlopen(3), and the raw tcti-name value is used for the lookup. Thus, this could be a path to the shared library, or a library name as understood by dlopen(3) semantics.

Tcti Options

This collection of options are used to configure the various known TCTI modules available:


To list the fixed properties of the TPM

tpm2_getcap properties-fixed

To list the supported capability groups

tpm2_getcap -l


Tools can return any of the following codes:


Github Issues (


See the Mailing List (

Referenced By

systemd-cryptenroll(1), tpm2_create(1).

tpm2-tools General Commands Manual