Zone Defined

A zone in Fibre Channel is a segment of a fabric that is composed of selected targets and initiators. Like with a  VLAN, only the members of a zone have access to one another.  Simply because the switch allows the members to access one another doesn’t mean you can’t still limit access more granularly.  You can use storage-based filters, such as LUN Masking, for which devices can access one another based on WWNN information from the initiator port. With Xsan, you can use LUN Masking to limit which of the hosts on your SAN have access to your Xserve RAIDs. UPDATE: LUN Masking was removed as a feature from the Xserve RAID.

On the Road: New Jersey

Jersey is weird.  There are a lot of different communities that are close to one another but all very different.  There are parts that are basically an extension of Philadelphia and others that are basically an extension of New York.  Then there is Atlantic City and the Shore.  And if you’re there and you don’t go see Lucy the Elephant then you just don’t miss what you’re missing.  But don’t forget, if you end up there, make sure to clean up your aunt’s floor…

Using a + in an email address

If you take an email address like my iCloud account, it’s krypted@me.com. If I take the username and add a + at the end I can then type some characters and put it all in front of the @ and domain name then the mail will still come to me. So, let’s say I use it to create an AppleID for an APNS certificate. That would be: krypted+apns@mac.com Or iTunes: krypted+itunes@mac.com Or iPhone1 (or these days iPad1): krypted+ipad1@mac.com The only gotcha is that occasionally you’ll run into some field on a webpage that has input validation for non alpha-numeric characters. Shouldn’t be the case, but it comes up from time to time. I use this a lot. For example, rather than use my email w/ my credit card company, I can use krypted+SOMECOMPANY@me.com and then I can create filters in Mail a little more easily for mail that comes from them. The best part about that is that it then shows me really easily who is selling my information that shouldn’t. For example, you’d think SOMECOMPANY gets enough $ out of me as a paying customer, but apparently not because they’ve sold my email address to at least 3 or 4 companies.

The basics of cron

 The cron command has officially been deprecated in Mac OS X, but still functions if called upon. cron starts a process that executes commands at specified dates and times. Regularly scheduled commands can be specified according to instructions found in the crontab files in the directory /var/spool/cron/crontabs. Users can submit their own crontab files via the crontab command.  Crontab copies the specified file or standard input if no file is specified, into a directory that holds all users’ crontabs.  crontab options:
  • The -e option edits a copy of the current users’ crontab file or creates an empty file to edit if crontab does not exist.
  • The-r option removes a user’s crontab from the crontab directory.
  • The -l options lists the crontab file for the invoking user.
A crontab file consists of lines of six fields each.The fields are separated by spaces or tabs. The first five are integers that specify the following (in order):
  • minute (0-59)
  • hour (0-23)
  • day of the month (1-31)
  • month of the year (1-12)
  • day of the week (0-6 with 0=Sunday)
Each of these patterns may be either an asterisk (meaning all valid values) or a list of elements separated by commas. An element is either a number or two numbers separated by a minus sign ( meaning an inclusive range). Notice the time is in 24 hour format, 0 is midnight and 13 is one in the afternoon.  The * wildcard can be used to run on every instance of a given object. The sixth field of a line in a crontab file is a string to be executed by the shell at the specified times by the first fife fields. A percent character in this field (unless escaped by ) is translated to a newline character. Only the first line (up to a % or end of line) of the command field is executed by the shell. The other lines are made available to the command as standard input. Any line beginning with a # is a comment and is ignored.