If they are the same we may end up with more than one host derotated.

The problem is as follows:  as soon as shutdown runs, mininag derotated the
host.  So we start at time T, host a starts its shutdown, gets derotated, at
T+30 reboots and at T+40 mininag likes it again.  Host b starts its shutdown at
time T+30 and thus gets derotated.  So between T+30 and T+40, we will not like
a nor b.

howto/upgrades.md

@@ -145,7 +145,7 @@ defined to `justdoit` or `rotation`:
     ./reboot -H $(ssh alberti.torproject.org 'ldapsearch -h db.torproject.org -x -ZZ -b ou=hosts,dc=torproject,dc=org -LLL "(rebootPolicy=justdoit)" hostname | awk "\$1 == \"hostname:\" {print \$2}" | sort') --delay-hosts=30 --delay-shutdown=10 -v
 
     echo "rebooting 'rotation' hosts with a 30-minute delay...."
-    ./reboot -H $(ssh alberti.torproject.org 'ldapsearch -h db.torproject.org -x -ZZ -b ou=hosts,dc=torproject,dc=org -LLL "(rebootPolicy=rotation)" hostname | awk "\$1 == \"hostname:\" {print \$2}" | sort') --delay-hosts=30 --delay-shutdown=30 -v
+    ./reboot -H $(ssh alberti.torproject.org 'ldapsearch -h db.torproject.org -x -ZZ -b ou=hosts,dc=torproject,dc=org -LLL "(rebootPolicy=rotation)" hostname | awk "\$1 == \"hostname:\" {print \$2}" | sort') --delay-hosts=30 --delay-shutdown=10 -v
 
 The remaining is the "manual" procedure, the KVM hosts: