DEVELOPER_NOTES: update board lockfile info

DEVELOPER_NOTES.rst

@@ -1,39 +1,17 @@
 Sharing development boards
 ==========================
 
-To avoid conflicts for development boards on the server, while using a board you must hold the corresponding lock file present in ``/var/lib/artiq/boards``. Holding the lock file grants you exclusive access to the board.
+To avoid conflicts for development boards on the server, while using a board you must hold the corresponding lock file present in the ``/tmp`` folder of the machine to which the board is connected. Holding the lock file grants you exclusive access to the board.
 
-To lock the KC705 for 30 minutes or until Ctrl-C is pressed:
+For example, to lock the KC705 until ENTER is pressed:
 ::
-  flock --verbose /var/lib/artiq/boards/kc705-1 sleep 1800
-
-Check that the command acquires the lock, i.e. prints something such as:
-::
-  flock: getting lock took 0.000003 seconds
-  flock: executing sleep
-
-To lock the KC705 for the duration of the execution of a shell:
-::
-  flock /var/lib/artiq/boards/kc705-1 bash
-
-You may also use this script:
-::
-  #!/bin/bash
-  exec flock /var/lib/artiq/boards/$1 bash --rcfile <(cat ~/.bashrc; echo PS1=\"[$1\ lock]\ \$PS1\")
+  ssh rpi-1.m-labs.hk "flock /tmp/board_lock-kc705-1 -c 'echo locked; read; echo unlocked'"
 
 If the board is already locked by another user, the ``flock`` commands above will wait for the lock to be released.
 
-To determine which user is locking a board, use:
+To determine which user is locking a board, use a command such as:
 ::
-  fuser -v /var/lib/artiq/boards/kc705-1
-
-
-Selecting a development board with artiq_flash
-==============================================
-
-The board lock file also contains the openocd commands for selecting the corresponding developer board:
-::
-  artiq_flash -I "$(cat /var/lib/artiq/boards/sayma-1)"
+  ssh rpi-1.m-labs.hk "fuser -v /tmp/board_lock-kc705-1"
 
 
 Deleting git branches