remctl Java Implementation


This directory contains a remctl implementation written in Java. Both a client and a server are included, and the implementation supports version two of the remctl protocol. Both client and server are written natively in Java and are entirely independent of the C implementation.

This implementation is not as mature or as well-tested as the C implementation. Any feedback and bug reports are gratefully accepted.


This implementation works with the Sun Java JDK 1.4.2, 5, and 6. It will not build with gcj; it could be ported, but wouldn't be useful until gcj has or an equivalent.

You can use either the provided simple Makefile or ant to build the JAR file. This source tree will also build in Eclipse and includes an Eclipse .project and .classpath file.

To use 256-bit AES keys, you will need to get the "Java Cryptography
Extension (ECE) Unlimited Strength Jurisdiction Policy Files 6"
(filename, which is available (at least to US
residents) from


If you have ant available, it's the easiest way to build the JAR file. Running ant dist will build the JAR file and put it in dist/lib. You may have to set ANT_HOME and JAVA_HOME to point ant at the appropriate directories.

If you do not have ant, you can use the provided Makefile, which will create the JAR file in the current directory. If your JDK isn't at /usr/lib/jvm/java-6-sun, either edit the Makefile to change JAVA_HOME and then run make, set the JAVA_HOME variable on the command line with:

    make JAVA_HOME=/path/to/jdk

or set JAVA_HOME in the environment.

However you do the build, create a k5.conf file by copying your /etc/krb5.conf file and then adding these lines to the [libdefaults] section:

default_tgs_enctypes = des3-hmac-sha1 des-cbc-crc des-cbc-md5 default_tkt_enctypes = des3-hmac-sha1 des-cbc-crc des-cbc-md5 permitted_enctypes = des3-hmac-sha1 des-cbc-crc des-cbc-md5

MIT Kerberos and Heimdal do not need this configuration and it is wrong for them, but the built-in list for Sun Java is limited and it will break if it encounters encryption types that it doesn't understand. The sample k5.conf in this directory can be used, but change the default realm.

You can remove the DES enctypes if your realm doesn't support DES. If you are using Java 6, you can add aes128-cts to the beginning of each list. If you have the file installed, you can also add aes256-cts to the beginning of each line.


You can now run the client from the JAR file:

    java \ -jar remctl-*.jar \
        <host> <command> <subcommand> [<parameter> ...]

This connects to the remctld on <host> and sends the command <type> <service> <parameter>. If you're using ant, the JAR file will be in dist/lib instead. You can also run the client from the class files:

    java \ \
        -cp build:. org.eyrie.eagle.remctl.RemctlClient \
        <host> <command> <subcommand> [<parameter> ...]

Also look at for an example of how to use the class in a Java program.

To run the server, create a keytab that the server will use for authentication and revise bcsKeytab.conf to match (you will need to change the principal at least). Then, start the server with:

    java \ -cp build:. \
        t7 4373 <principal>

This will start the server defined in, which just returns information about what command it received. 4373 is the port to listen to (4373 is the default value for remctl). Replace <principal> for the principal you created a keytab for.

To run this from Eclipse, select from the Run, Run..., "java application", make an instance for the selected Main Class. Under Arguments, set VM arguments to be those above for "java", and set the program arguments to be everything past the jar file or main class.


The java directory of the remctl distribution is not structured like a conventional Java distribution. However, you can generate an independent source distribution that looks much more like a standard Java distribution using ant. Optionally first run ant dist to build the JAR file and then run ant tar to generate the distribution (which will then be found in dist). This generated distribution will be structured like an Apache Jakarta project:

    dist/lib          The built JAR file with the version in its name
    doc               This documentation and the sample configuration
    src               The JAR file source

The running instructions above will be slightly different if you use this distribution, since the configuration files will be in doc instead of at the top level and the test Java files will be in bin.


This Java remctl implementation was written by Marcus Watts, based somewhat on the original remctl Java implementation by Anton Ushakov. The build system and this documentation is based on the build system and documentation provided by Marcus.


Copyright 2007-2010 The Board of Trustees of the Leland Stanford Junior University

Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved. This file is offered as-is, without any warranty.

SPDX-License-Identifier: FSFAP

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