Mounting Linux LVM drives

Because my Thinkpad X200 has finally, after just under 3 years, decided to give up the ghost via a FAN ERROR and refusal to start (POST beeps & auto-shutdown), I'm now faced with the task of recovering all the data on the drive (about 120G) across multiple partitions.

Here's the drive layout, as per cfdisk:

                                   cfdisk (util-linux-ng 2.17.2)

                                        Disk Drive: /dev/sdb
                                 Size: 160041885696 bytes, 160.0 GB
                       Heads: 255   Sectors per Track: 63   Cylinders: 19457

     Name           Flags         Part Type    FS Type              [Label]            Size (MB)
 --------------------------------------------------------------------------------------------------
     sdb1                          Primary     NTFS                 [^B]                26214.44   *
     sdb2           Boot           Primary     Linux ext3                                 209.72   *
                                   Logical     Free Space                                   3.68   *
     sdb5                          Logical     Linux ext3           [HOME]             106043.70   *
     sdb6           NC             Logical     Linux LVM                                20970.48   *
                                   Logical     Free Space                                   1.09   *
     sdb4                          Primary     Compaq diagnostics                        6595.71   *
                                               Unusable                                     0.49   *

So, under a Fedora 13 LiveCD, the /boot (sdb2) and /home (sdb5) partitions automounted, along with the WinXP (sdb1) partition. But the root partition (/, part of sdb6) would not as it's part of a LVM. After a quick burst of googling, I found this solution, which digests down to simply this:

yum install lvm2 -y; # install support for lvm2
pvscan # scan vol groups
vgchange vg_x2lappy -a y # mark your vol group active
lvscan # scan for logical volumes 
mkdir /media/sdb6 # create a mount point
mount /dev/vg_x2lappy/lv_root /media/sdb6/ # mount the lv
cd /media/sdb6/; ls -la # take off every zig!

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

Hudson & Virtual Box: Creating a common share with SSHFS

I've been working a recently with my own Hudson server, setting up Fedora and OpenSolaris images as slave nodes to prototype new ways to build. Tonight I found a very handy trick for mounting shared drives using SSHFS. Kudos to the man page writers -- all the tips I found via Google were outdated or just plain wrong. man sshfs to the rescue!

Step 1: create a folder on the Hudson master / Virtual Box host with files you want to share, eg., /shared

Step 2: create an empty folder on each Hudson slave / Virtual Box guest as a mount point for the shared folder, eg., /shared

Step 3: on the guest, install sshfs, eg., sudo yum install fuse-sshfs.

Step 4: mount the share: sshfs user@hudson-master-host.your-domain.com:/shared /shared

Of course you'll probably want to set up ssh keys and add this to your startup scripts so that the mount happens automatically when the guest is launched, but I'll leave that for next time.