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tpm2_readclock - Man Page

Retrieves the time information from the TPM.


tpm2_readclock [OPTIONS]


tpm2_readclock(1) -Reads the current TPMS_TIME_INFO structure from the TPM. The structure contains the current setting of Time, Clock, resetCount, and restartCount. The structure is output as YAML to stdout. The YAML output is defined as:

time: 13673142     # 64 bit value of time TPM has been powered on in ms.
  clock: 13673142  # 64 bit value of time TPM has been powered on since last TPM2_Clear in ms.
  reset_count: 0   # 32 bit value of the number of TPM Resets since the last
                   # TPM2_Clear.
  restart_count: 0 # 32 bit value of the number of times that TPM2_Shutdown or
                   # _TPM_Hash_Start have occurred since the last TPM Reset or
                   # TPM2_Clear.
  safe: yes        # boolean yes|no value that no value of Clock greater than
                   # the current value of Clock has been previously reported by
                   # the TPM.

This tool takes no arguments and no tool specific options.


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:


Read the clock

time: 13673142
  clock: 13673142
  reset_count: 0
  restart_count: 0
  safe: yes


Tools can return any of the following codes:


Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)


See the Mailing List (https://lists.linuxfoundation.org/mailman/listinfo/tpm2)


tpm2-tools General Commands Manual