[archiso_pxe_nbd] Allow change NBD export name.

Requested at FS#25051
Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>

README

@@ -59,6 +59,8 @@ INDEX
                     when option "IPAPPEND" is set to 2 or 3 in config.
                     BOOTIF=<hardware-address-of-boot-interface>
                     Default: (set via PXELINUX)
+* archiso_nbd_name= Set NBD export name used by the server.
+                    Default: archiso
 
 
 ** hooks/archiso_loop_mnt

archiso/hooks/archiso_pxe_nbd

@@ -55,6 +55,8 @@ run_hook () {
 
         nbdserver=${rootserver}
 
+        [[ -z "${archiso_nbd_name}" ]] && archiso_nbd_name="archiso"
+
         mount_handler="archiso_pxe_nbd_mount_handler"
     fi
 }
@@ -74,9 +76,9 @@ archiso_pxe_nbd_mount_handler () {
 
     msg "::: Setup NBD from ${nbdserver} at /dev/nbd0"
     if [ "${copytoram}" = "y" ]; then
-        nbd-client ${nbdserver} -N archiso /dev/nbd0
+        nbd-client ${nbdserver} -N ${archiso_nbd_name} /dev/nbd0
     else
-        nbd-client ${nbdserver} -N archiso /dev/nbd0 -persist
+        nbd-client ${nbdserver} -N ${archiso_nbd_name} /dev/nbd0 -persist
     fi
 
     archisodevice=/dev/nbd0