====== Automounting usb drives is udev ======
I've a GoFlexNet that runs Slackware Arm that I like to use as NAS (nice to be able to do software raid with the 2 sata drives). Along with having an array I also wanted to be able to share any usb disk really quickly without having to interact in any way with the appliance: this is what I came up with:

The idea is to use the volume labels to have the usb drive mounted and exported via NFS. Any partition that has no label or that is linux swap will be ignored. Well the umounting upon drive unplug is pointless but it also cleans up the exported filesystems avoiding writes in the parent directory.

I wrote a couple of really simple udev rules to call the management program: 

  root@nas:~# cat /etc/udev/rules.d/99-persistent-personal.rules 
  ACTION=="add",KERNEL=="sd[a-z][1-9]", PROGRAM="automount"
  ACTION=="remove",KERNEL=="sd[a-z][1-9]", PROGRAM="automount"
  root@nas:~#
  
And this is the management script 

  root@nas:~# cat /lib/udev/automount 
  #!/bin/bash
  PATH=/bin:/usr/bin:/usr/local/bin:/sbin:/usr/sbin
  #echo "$(date) " >> /tmp/env.txt
  #/usr/bin/env >> /tmp/env.txt
  #id >> /tmp/env.txt
  DEV=$(basename $DEVNAME)
  LABEL=$(ls -l /dev/disk/by-label/ |grep $DEV |awk '{print $(NF-2)}')
  [ "$LABEL" = "" ] && LABEL=$ID_FS_LABEL
  [ "$LABEL" = "" ] && exit
  [ "$ID_PART_ENTRY_TYPE" = "0x82" ] && exit
  
  echo "$DEV $LABEL $ACTION" >> /tmp/env.txt
  
  case $ACTION in
  add) mkdir -p /mnt/exports/$LABEL
       logger "automount: add $LABEL"
       exportfs -u *:/mnt/exports/$LABEL
       mount LABEL=$LABEL /mnt/exports/$LABEL
       [ $(grep -c "^/mnt/exports/$LABEL" /etc/exports) -eq 0 ] && \
         echo "/mnt/exports/$LABEL *(rw,no_root_squash,no_subtree_check,nohide)" >> /etc/exports
       exportfs -r -a 
    ;;
  remove) 
       logger "automount: remove $LABEL"
       exportfs -u *:/mnt/exports/$LABEL
       mount -o remount,ro /mnt/exports/$LABEL
       umount /mnt/exports/$LABEL
       rmdir /mnt/exports/$LABEL
  ;;
  esac
  
  root@nas:~#
  
This is what my /etc/exports looks like initially:

  root@nas:~# cat /etc/exports 
  # See exports(5) for a description.
  # This file contains a list of all directories exported to other computers.
  # It is used by rpc.nfsd and rpc.mountd.
  /mnt/exports *(rw,no_root_squash,no_subtree_check,crossmnt)
  root@nas:~#

it gets populated with new lines as the usb drives come and go. The only thing you may want to do before unplugging any usb drive is remounting the filesystem ReadOnly on the nas manually. There aren't any buttons on the GoFlexNet that can be used to tigger this unfortunately,
====== Sources ======
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