#### Beyond Linux® From Scratch (System V Edition) - Version 12.3

### Chapter 13. Programming

- Prev

  OpenJDK-23.0.2

- Next

  apache-ant-1.10.15

- Up
- Home

# Configuring the Java environment

## Setting up the environment

After the package installation is complete, the next step is to make sure that the system can properly find the files. If you set up your login scripts as recommended in The Bash Shell Startup Files, update the environment by creating the `openjdk.sh` script, as the `root` user:

    cat > /etc/profile.d/openjdk.sh << "EOF"
    # Begin /etc/profile.d/openjdk.sh

    # Set JAVA_HOME directory
    JAVA_HOME=/opt/jdk

    # Adjust PATH
    pathappend $JAVA_HOME/bin

    # Auto Java CLASSPATH: Copy jar files to, or create symlinks in, the
    # /usr/share/java directory.

    AUTO_CLASSPATH_DIR=/usr/share/java

    pathprepend . CLASSPATH

    for dir in `find ${AUTO_CLASSPATH_DIR} -type d 2>/dev/null`; do
        pathappend $dir CLASSPATH
    done

    for jar in `find ${AUTO_CLASSPATH_DIR} -name "*.jar" 2>/dev/null`; do
        pathappend $jar CLASSPATH
    done

    export JAVA_HOME

    # By default, Java creates several files in a directory named
    # /tmp/hsperfdata_[username]. This directory contains files that are used for
    # performance monitoring and profiling, but aren't normally needed on a BLFS
    # system. This environment variable disables that feature.
    _JAVA_OPTIONS="-XX:-UsePerfData"

    export _JAVA_OPTIONS

    unset AUTO_CLASSPATH_DIR dir jar _JAVA_OPTIONS

    # End /etc/profile.d/openjdk.sh
    EOF

If Sudo-1.9.16p2 is installed, the super user should have access to the above variables. Execute the following commands as the `root` user:

    cat > /etc/sudoers.d/java << "EOF"
    Defaults env_keep += JAVA_HOME
    Defaults env_keep += CLASSPATH
    Defaults env_keep += _JAVA_OPTIONS
    EOF

To use mandb to include the OpenJDK man pages in its database, issue, as the `root` user:

    cat >> /etc/man_db.conf << "EOF" &&
    # Begin Java addition
    MANDATORY_MANPATH     /opt/jdk/man
    MANPATH_MAP           /opt/jdk/bin     /opt/jdk/man
    MANDB_MAP             /opt/jdk/man     /var/cache/man/jdk
    # End Java addition
    EOF

    mkdir -p /var/cache/man &&
    mandb -c /opt/jdk/man

## Setting up the Certificate Authority Certificates for Java

OpenJDK uses its own format for the CA certificates. The Java security modules use `$JAVA_HOME``/lib/security/cacerts` by default. In order to keep all the certificates in one place, we use `/etc/ssl/java/cacerts`. The instructions on the make-ca-1.15 page previously created the file located in `/etc/ssl/java`. Set up a symlink in the default location as the `root` user:

    ln -sfv /etc/pki/tls/java/cacerts /opt/jdk/lib/security/cacerts

Use the following command to check if the `cacerts` file has been successfully installed:

    /opt/jdk/bin/keytool -list -cacerts

At the prompt `Enter keystore password:`, enter `changeit` (the default) or just press the “Enter” key. If the `cacerts` file was installed correctly, you will see a list of the certificates with related information for each one. If not, you need to reinstall them.

If you later install a new JVM, you just have to create the symlink in the default location to be able to use the cacerts.

- Prev

  OpenJDK-23.0.2

- Next

  apache-ant-1.10.15

- Up
- Home