When we transfer certain amounts of data in a packet we might cause that packet to fragment. The less fragmentations without requiring a collision or a re-send of a packet, the more efficient network traffic can be. The MTU defines the packet size. Different types of data or network links respond differently. To change the MTU on a Windows Server we’re going to use the netsh command. First, we’re going to use ping to ping a host on our network, using -f and then -l which allows us to define the MTU size. In this case we’re going to use 1500: ping https://krypted.com/ -f -l 1500 We should get an…
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APIPA, Not Just An Acronym Palindrome
The acrodrome (yes, I just made that up, although I wasn’t sure if palinym was a better choice – decided on acrodome because I wasn’t as afraid of Tea Party snipers coming to murder me as I would have been if I used palinym) APIPA stands for Automatic Private IP Addressing. APIPA is in every version of Windows since NT and all versions of Mac OS X. APIPA is a dhpc mechanism that provides dhcp clients with self-assigned IP addresses when DHCP servers are not available. When there isn’t a DHCP server available, APIPA assigns IPs from 169.254.0.1 to 169.254.255.254 with a default mask of 255.255.0.0. Clients leverage arp to…
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16 Child Proofing iPad and iPod Touch Tips For Parents
Recently I woke up and my daughter was sitting on me watching something on the iPad. As I woke ever so slightly I realized that she was watching Transformers the movie on Netflix. I’m not typically a helicopter dad, hovering over her every move, but I did realize amidst the explosions that ya’, I might want to take some of the things I learned writing the book on locking these things down and put a few very basic measures in place to keep her from seeing something she shouldn’t. After all, she’s gotten about as good at navigating around the thing as I am (and these days she’s getting pretty…
- cloud, FileMaker, Mac OS X, Mac OS X Server, Mac Security, Mass Deployment, Network Infrastructure, Time Machine, Xsan
Obtain Information From Watchman Monitoring Using a Script
Watchman Monitoring is a tool used to monitor computers. I’ve noticed recently that there’s a lot of traffic on the Watchman Monitoring email list that shows people want a great little (and by little I mean inexpensive from a compute time standpoint) monitoring tool to become a RMM (Remote Management and Monitoring) tool. The difference here is in “Management.” Many of us actually don’t want a monitoring tool to become a management tool unless we are very deliberate about what we do with it. For example, that script that takes a machine name of ‘rm -Rf /’ that some ironic hipster of a user decided to name their hard drive…
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When Packets Are Too Large in MySQL
Every now and then you’ll see an error like “Packet Too Large” in MySQL, as seen below. When you run into this, you’re trying to shove more information into a given SQL statement than is allowed. So to fix, you have a few different options, starting with the best, which is to make your SQL better. But not everyone has control of things like source code. So you might need to change the value in mysql itself. To do so, simply run the mysql command with the –max_allowed_packet and then put = followed by the size of the packet. For example, to make it 128: mysql --max_allowed_packet=128M Now, by default…
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Managing DNS In Windows Server 2012
Previously, I covered installing the DNS role in Windows Server 2012. Once installed, managing the role is very similar to how management was done in Windows Server 2003 through 2008 R2. With the exception of how you access the tools. DNS is one of the most important services in Windows Servers, as with most other platforms. So it’s important to configure DNS. To get into the DNS Manager in 2012 Server, first open Server Manager (you might get sick of using this tool in Server 2012, similar to how my Mac Server brethren have gotten tired of it in Lion and Mountain Lion Servers. Then from Server Manager click on…
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A Little More About afctl in OS X Server
Awhile back I wrote an article on managing the Adaptive Firewall built into Mountain Lion Server at https://krypted.com//mac-os-x-server/managing-lion-servers-adaptive-firewall-from-the-command-line. It’s worth mentioning that when you use this command you’re basically editing some text files. These include the blacklist, blockedHosts and whitelist folders at possibly the shortest folder at this depth in the file system that I’ve ever had the good luck to need to use /var/db/af (okay, okay, I’m sure we’ve all made /a/b/c and that’s shorter, but this is pretty close). You should use afctl to add and remove machines from these lists. The -w option in afctl used to add a host to a whitelist will cause the host…
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Aerohive Status Color Codes
Ever wonder what those color codes on on all your devices mean while they’re booting up? In the IT industry we went from having beep tones and green lights to now having all kinds of methods including touch screens on printers that are as nice as my iPhone practically, computers with touch screens that indicate POST status and of course LEDs that change colors. The LEDs that change colors can be extra special, because we assume yellow is bad, green is good, blue is good and red is really bad. Aerohive uses a different color scheme, which can be a little confusing at first. So what do their LEDs mean?…
- Active Directory, Mac OS X, Mac OS X Server, Mac Security, Network Infrastructure, Ubuntu, Unix, VMware, Windows Server, Windows XP, Xsan
List All DNS Records For A Domain
Sometimes you want to move a domain but you don’t have a copy of the zone file in order to recreate records. The easy way to do this is to grab a zone transfer. To do so, dig is your friend: dig -tAXFR mycompany.com Sometimes though (and actually more often than not) a zone transfer is disabled. In that case you’ll need to dig the domain a bit differently. I like to use +nocmd, query for any and list the results (+answer): dig +nocmd https://krypted.com/ any +answer Which results in the following: ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 39183 ;; flags: qr rd ra; QUERY: 1,…
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Using the XenSource Command Line Interface
XenSource has some pretty good GUI tools. There’s XenCenter and the xsconsole, both of which are pretty adequate in a free sense and get pretty darn interesting when you actually pay Citrix. But today I want to take a little look under the hood of XenSource. I had previously written about Xen. But note that this is a different beast. Before I get started talking about how to do some tasks in XenSource, I first want to throw out there a few terms. The first, is virtual machine. This is exactly what it sounds like, an operating system that runs on a virtual host rather than a physical hosts. So…