Written 2004–2016 by Wayne Pollock, Tampa Florida USA. All Rights Reserved.
Much of this material was adapted from The Practice of System and Network Administration by Limoncelli and Hogan. ©2002 by Lumeta Corp. and Christine Hogan. Published by Addison-Wesley.liveor
productionsystem.
breakexisting applications. Never be the first to install some patch — let someone else find the problems with it! Wait at least a few days even for a
criticalor security patch. Wait a few weeks before applying a kernel patch.
try just one more thing.
Even this type of change needs planning in advance.
Hosts and remote DNS servers will cache IP
address for a long time, usually days.
This cache time is set on your DNS server;
it's called the time to live (TTL
) value.
TTL days before an IP change cut-over,
change the TTL to one day.
The day before the cut-over, change the TTL again to
5 minutes or whatever interval of time you deem appropriate for users
to start using the new service.
After the cut-over is deemed successful, change the TTL
back to the original value.
That's the day of the demonstration to the customer).
That is a term used to describe something extra. In this case it means add extra time. Say you think something will take one hour. Don't tell users (or your boss) one hour, add a fudge factor of, say, 15 minutes or more.
The fudge factor allows for the situation when something takes longer than you estimated. You don't want to go over the time you told others it will take to complete some task. As a new system administrator you generally add a big fudge factor (say double your original estimate). As you gain experience, you generally add smaller and smaller fudge factors.
The concept applies to everything, not just time. If you have a budget request for new equipment for $122.00, then you should add a fudge factor and ask for a budget of $130.00 (or even $150.00 if you can get away with that). When the price at CompUSA changes on you, you won't need to request a budget all over again as long as the new price is below your original request. The concept applies to the maximum load of elevators (only in that case they call it a safety factor), the amount of cable you would need to purchase to wire a network, and so on. Back