$ ./kshold e1 e0 echo tty0 &
  Name: tty0  Type: echo  ID: 000000dc  Num hooks: 1
$ ./ttyprobe
slave /dev/pts/0 initial line discipline: 0
TIOCSETD NETGRAPHDISC #1 (colliding node exists): rc=-1 errno=48 (Address already in use)
discipline now: 0 (expected unchanged 0)
TIOCSETD NETGRAPHDISC #2: rc=0 errno=0 (ok)
restore discipline 0: rc=0
TTYPROBE-DONE guest alive
# syslog: "kernel: tty0: node name exists?"  (ng_tty.c:227 - the error branch)