For some reasons, you may want to modify the TTL (Time to Live) of a DNS Server.

The default TTL is 10800 seconds (3 hours).  To modify the TTL, edit the following file on your OS X DNS Server and replace $TTL 10800 with the $TTL value you desire.  Please note using a TTL value of 0 (zero) is not supported by some systems and is not advised.

The DNS cache on the client systems may need to be flushed to honor the new TTL.  This is done on OS X by using the “dscacheutil -flush” command.

vi /var/named/zones/db.cloudmac.net.zone.apple

Here is an example config file:

dns1:~ root# cat /var/named/zones/db.cloudmac.net.zone.apple
 ;GUID=D521C96D-AA85-4438-A1BC-8B1D7987DCD0
 ;selfResolvingHostname=0

$TTL 300
cloudmac.net. IN SOA dns.cloudmac.net. netopps.cloudmac.net. (
     2011112804    ;Serial
     86400         ;Refresh
     3600          ;Retry
     604800        ;Expire
     345600        ;Negative caching TTL
 ) 

cloudmac.net. IN  NS dns.cloudmac.net.
dns1 IN  A 10.22.100.30
mail IN  A 10.22.100.31
cloudmac.net. IN  MX 0 mail.cloudmac.net.
dns1:~ root#

Run the dig command to confirm the TTL information reflects what you entered:

dns1:~ root# dig mail.cloudmac.net @10.22.100.30

; <<>> DiG 9.6-ESV-R4-P3 <<>> mail.cloudmac.net @10.22.100.30
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 983
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1

;; QUESTION SECTION:
;mail.cloudmac.net.        IN    A

;; ANSWER SECTION:
mail.cloudmac.net.    300    IN    A    10.22.100.31

;; AUTHORITY SECTION:
cloudmac.net.        300    IN    NS    dns1.cloudmac.net.

;; ADDITIONAL SECTION:
dns1.cloudmac.net.    300    IN    A    10.22.100.30

;; Query time: 1 msec
;; SERVER: 10.22.100.30#53(10.22.100.30)
;; WHEN: Mon Nov 28 16:47:32 2011
;; MSG SIZE  rcvd: 85

dns1:~ root#

More info is available by following the links below:

Time to live (TTL) – Wikipedia.com

DNS Round Robin – Wikipedia.com

dscacheutil – developer.apple.com

http://bluearc.com/storage-news/press-releases/110907-Hitachi-Data-Systems-Announces-Acquisition-of-BlueArc.shtml

Check CloudMac.net for details.

Operating Systems Offered:

• OS X Snow Leopard (10.6)

• OS X Snow Leopard Server – Unlimited (10.6)

• CentOS Linux

• RedHat Enterprise Server

• Windows 2008 Server

Hardware Offerings:

• Mac mini
• Mac Pro
• SuperMicro

More information is available on our website:

http://oneiricsys.com/services/dedicated-servers/

Please contact us for pricing inquiries.

This update includes the Mac App Store, a new application you’ll find in the Dock. The Mac App Store includes the following features:

• Discover Mac apps: Browse featured apps, top charts, and categories; or, search for something specific. Read detailed app descriptions and user reviews, and flip through screen shots.

• Buy and install: Easily purchase apps with your iTunes account. Apps install in one step and are quickly available from the Dock.

• App updates: The Mac App Store keeps track of all your purchased apps and notifies you when free updates are available.

Additional improvements

• Fixes a DNS resolution issue for Mac OS X Server v10.6.5. The system now properly resolves a DNS alias (CNAME) that points to a host in a .local domain.

• Improves Mac OS X Server security. For more information about the security content of Mac OS X Server v10.6.5 see this article.

• Includes all the improvements in the previous 10.6.1, 10.6.2, 10.6.3, 10.6.4 and 10.6.5 updates.

• Mac OS X Server v10.6.6 also includes all improvements delivered in the client Mac OS X v10.6.6 Update.

More information is available on Apple’s site: http://support.apple.com/kb/HT4460

As always, all hosting options are month-to-month with $0 setup fee.  For more info, please visit http://cloudmac.net/l/july_special

Offer available while servers are available.

For more information, please refer to the site and CloudMac blog.

ethtool -i eth0

Execute the command to clear the counters.  This command assumes the driver e1000:

modprobe -r e1000; modprobe e1000; ifup eth0

Confirm the command was successful:

ifconfig eth0 | grep bytes
RX bytes:1400246 (1.3 MiB)  TX bytes:58638 (57.2 KiB)

From the output above, the RX and TX bytes were cleared and only display traffic from the last couple of seconds.

*Disclaimer: Use warning performing these commands if unsure of the proper syntax / variables.  Misuse will result in “disconnecting the astronaut” and losing access to the remote host.

Overall, we are very impressed with the Thinklogical unit.