Section: GNU Privacy Guard (1)
Updated: 2009-09-04
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scdaemon - Smartcard daemon for the GnuPG system  


scdaemon [--homedir dir] [--options file] [options] --server
scdaemon [--homedir dir] [--options file] [options] --daemon [command_line]



The scdaemon is a daemon to manage smartcards. It is usually invoked by gpg-agent and in general not used directly.



Commands are not distinguished from options except for the fact that only one command is allowed.

Print the program version and licensing information. Not that you can abbreviate this command.

--help, -h
Print a usage message summarizing the most useful command-line options. Not that you can abbreviate this command.

Print a list of all available options and commands. Not that you can abbreviate this command.

Run in server mode and wait for commands on the stdin. This is default mode is to create a socket and listen for commands there.

Run in server mode and wait for commands on the stdin as well as on an additional Unix Domain socket. The server command GETINFO may be used to get the name of that extra socket.

Run the program in the background. This option is required to prevent it from being accidentally running in the background.



--options file
Reads configuration from file instead of from the default per-user configuration file. The default configuration file is named oqscdaemon.confcq and expected in the oq.gnupgcq directory directly below the home directory of the user.

--homedir dir
Set the name of the home directory to dir. If this option is not used, the home directory defaults to oq~/.gnupgcq. It is only recognized when given on the command line. It also overrides any home directory stated through the environment variable oqGNUPGHOMEcq or (on W32 systems) by means of the Registry entry HKCU\Software\GNU\GnuPG:HomeDir.

Outputs additional information while running. You can increase the verbosity by giving several verbose commands to gpgsm, such as aq-vvaq.

--debug-level level
Select the debug level for investigating problems. level may be one of:

no debugging at all.
some basic debug messages
more verbose debug messages
even more detailed messages
all of the debug messages you can get

How these messages are mapped to the actual debugging flags is not specified and may change with newer releases of this program. They are however carefully selected to best aid in debugging.

All debugging options are subject to change and thus should not be used by any application program. As the name says, they are only used as helpers to debug problems.

--debug flags
This option is only useful for debugging and the behaviour may change at any time without notice. FLAGS are bit encoded and may be given in usual C-Syntax. The currently defined bits are:

0 (1)
command I/O
1 (2)
values of big number integers
2 (4)
low level crypto operations
5 (32)
memory allocation
6 (64)
7 (128)
show memory statistics.
9 (512)
write hashed data to files named dbgmd-000*
10 (1024)
trace Assuan protocol
11 (2048)
trace APDU I/O to the card. This may reveal sensitive data.

Same as --debug=0xffffffff

--debug-wait n
When running in server mode, wait n seconds before entering the actual processing loop and print the pid. This gives time to attach a debugger.

Enable debug output from the included CCID driver for smartcards. Using this option twice will also enable some tracing of the T=1 protocol. Note that this option may reveal sensitive data.

This option disables all ticker functions like checking for card insertions.

For security reasons we won't create a core dump when the process aborts. For debugging purposes it is sometimes better to allow core dump. This options enables it and also changes the working directory to oq/tmpcq when running in --server mode.

This option appends a thread ID to the PID in the log output.

Don't detach the process from the console. This is mainly useful for debugging.

--log-file file
Append all logging output to file. This is very helpful in seeing what the agent actually does.

--pcsc-driver library
Use library to access the smartcard reader. The current default is oqlibpcsclite.socq. Instead of using this option you might also want to install a symbolic link to the default file name (e.g. from

--ctapi-driver library
Use library to access the smartcard reader. The current default is oqlibtowitoko.socq. Note that the use of this interface is deprecated; it may be removed in future releases.

Disable the integrated support for CCID compliant readers. This allows to fall back to one of the other drivers even if the internal CCID driver can handle the reader. Note, that CCID support is only available if libusb was available at build time.

--reader-port number_or_string
This option may be used to specify the port of the card terminal. A value of 0 refers to the first serial device; add 32768 to access USB devices. The default is 32768 (first USB device). PC/SC or CCID readers might need a string here; run the program in verbose mode to get a list of available readers. The default is then the first reader found.

To get a list of available CCID readers you may use this command:

echo scd getinfo reader_list | gpg-connect-agent --decode | awk '/^D/ {print $2}'

--card-timeout n
If n is not 0 and no client is actively using the card, the card will be powered down after n seconds. Powering down the card avoids a potential risk of damaging a card when used with certain cheap readers. This also allows non Scdaemon aware applications to access the card. The disadvantage of using a card timeout is that accessing the card takes longer and that the user needs to enter the PIN again after the next power up.

Note that with the current version of Scdaemon the card is powered down immediately at the next timer tick for any value of n other than 0.

Even if a card reader features a keypad, do not try to use it.

This option disables the use of admin class commands for card applications where this is supported. Currently we support it for the OpenPGP card. This commands is useful to inhibit accidental access to admin class command which could ultimately lock the card through wrong PIN numbers. Note that GnuPG versions older than 2.0.11 featured an --allow-admin command which was required to use such admin commands. This option has no more effect today because the default is now to allow admin commands.

--disable-application name
This option disables the use of the card application named name. This is mainly useful for debugging or if a application with lower priority should be used by default.

All the long options may also be given in the configuration file after stripping off the two leading dashes.



scdaemon supports the card applications as described below.


The OpenPGP card application ``openpgp''


This application is currently only used by gpg but may in future also be useful with gpgsm. Version 1 and version 2 of the card is supported.

The specifications for these cards are available at ( and (


The Telesec NetKey card ``nks''


This is the main application of the Telesec cards as available in Germany. It is a superset of the German DINSIG card. The card is used by gpgsm.


The DINSIG card application ``dinsig''


This is an application as described in the German draft standard DIN V 66291-1. It is intended to be used by cards supporting the German signature law and its bylaws (SigG and SigV).


The PKCS#15 card application ``p15''


This is common framework for smart card applications. It is used by gpgsm.


The Geldkarte card application ``geldkarte''


This is a simple application to display information of a German Geldkarte. The Geldkarte is a small amount debit card application which comes with almost all German banking cards.



$ scdaemon --server -v



There are a few configuration files to control certain aspects of scdaemons's operation. Unless noted, they are expected in the current home directory (see: [option --homedir]).

This is the standard configuration file read by scdaemon on startup. It may contain any valid long option; the leading two dashes may not be entered and the option may not be abbreviated. This default name may be changed on the command line (see: [option --options]).

If this file is present and executable, it will be called on veyer card reader's status changed. An example of this script is provided with the distribution

This file is created by sdaemon to let other applications now about reader status changes. Its use is now deprecated in favor of oqscd-eventcq.



gpg-agent(1), gpgsm(1), gpg2(1)

The full documentation for this tool is maintained as a Texinfo manual. If GnuPG and the info program are properly installed at your site, the command

info gnupg

should give you access to the complete manual including a menu structure and an index.