Hudson & Virtual Box, Part 2: Creating a common share with vboxsf

My experiment last week with sshfs came to a grinding halt when I realized that while the share works, and can be automatically started, the permissions do not work and Hudson can't actually use the sshfs share; also, I couldn't get sshfs to compile for OpenSolaris, so it's really a non-starter.

Next up was mount_nfs, but after fighting with that, /etc/nfs.conf and /etc/exports for a couple days off and on, I realized there's a much simpler solution using Virtual Box itself: vboxsf. Note that it's sf (shared folder) not fs (file system).

Thanks to David Herron for the inspiration.

Here's how to set up a vboxfs share:

1. Ignore the Virtual Box wiki which suggests that you can't just use a Shared Folder: you can.
2. Guest: Launch your guest, then install the Virtual Box Guest Additions onto it.
3. Host: Create a user and set its uid and gid to some value which can be created on the guest / slave. For example, on Mac OSX 10.5 Server, launch System Preferences > System > Accounts, and create a "hudsonbuild" user with User ID and Group ID set to 500.

   Note that uid 500 and gid 500 are the defaults for the first user on a Fedora system; on Ubuntu it's 1000; on other systems YMMV.

4. Host: Create a folder in the root of your host called /shared. Put some files there. Give it full write permissions, and set its ownership to the user who'll be sharing the files:

   find /shared -type f -exec chmod 666 \;
   find /shared -type d -exec chmod 777 \;
   chown -R 500:500 /shared

5. Host: Add a Shared Folder. NOTE: If your guest is running, shut it down or see the next item. From the Virtual Box GUI (on the host), select Settings > Shared Folders > New (+). Add a shared folder called "shared" mapped to /shared (or call it something else and map it to a different path on your host).
6. Guest: Alternatively, you can add a Shared Folder to a running guest from its Devices menu. Add a shared folder called "shared" mapped to /shared.
7. Guest: As root, create a folder on the guest called /shared. Leave it empty, but make sure it's owned by your user.
8. Guest: As root, add this to the guest's /etc/fstab:

   shared  /shared vboxsf  auto,exec,rw,uid=500,gid=500    0       0

9. Guest: As root, mount the share one of three ways:

   # mount everything in /etc/fstab
   mount -a
   
   # mount using mount (and optional -o options)
   mount -t vboxfs -o auto,exec,rw,uid=500,gid=500 shared /shared
   
   # mount using mount.vboxsf (and optional -w and -o options)
   /sbin/mount.vboxsf -w -o rw,uid=500,gid=500 shared /shared

10. Guest: If this mount doesn't start automatically when the VirtualBox guest is started, you can add one of the above commands to the script you use to start the Hudson slave, eg:

    !/bin/bash
    #
    # Init file for Hudson server daemon
    #
    # chkconfig: 2345 65 15
    # description: Hudson server
    
    # HOWTO:
    # 1. rename this file on target server (Hudson slave node) to /etc/init.d/hudson
    # 2. to enable this script to run on startup, as root type the following:
    #    Fedora: 
    #        chkconfig --add hudson; chkconfig --list hudson
    #    OpenSolaris:
    #         for n in 0 1 6;   do cd /etc/rc${n}.d; ln -s /etc/init.d/hudson K15hudson; done
    #         for n in 2 3 4 5; do cd /etc/rc${n}.d; ln -s /etc/init.d/hudson S65hudson; done
    #         svccfg add hudson; svcs | grep hudson
    
    RETVAL=0
    
    #run Hudson as a slave node
    java -jar /opt/hudson/slave.jar -jnlpUrl \
      http://vboxsvr:8080/computer/${slaveNodeName}/slave-agent.jnlp &
    
    /sbin/mount.vboxsf -w shared /shared &
     
    exit $RETVAL