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Add user to Apache group www-data in Ubuntu

While working on an Ubuntu linux server yesterday I ran into a group permissions issue involving Apache2. The default Apache group in Ubuntu is www-data. To solve the problem, a user needed to be added to the www-data group. Figured I'd write up a quick post on how you can add a user to the www-data group. We'll use the username "bob" for the examples below.

Add an existing user to the www-data group

$ sudo usermod -a -G www-data bob

To verify, use the groups command:

$ groups bob
bob: adm bob cdrom sudo dip www-data plugdev lpadmin sambashare

Create a new user and add them to the www-data group

$ sudo useradd -g www-data bob

To verify, use the groups command:

$ groups bob
bob: www-data

How to flush dns cache on a mac

Mac Terminal

If you use a mac and need to flush the hosts local DNS cache there is a relatively simple way to accomplish this. Similar to the procedure on a Windows machine (open cmd and type ipconfig /flushdns), this procedure is done on a command line prompt.

To begin, open a terminal window

Then type the following command:

dscacheutil -flushcache

That's all there is to it. However, to make it simpler, I've created a script file on my desktop that can easily be double-clicked any time I need to flush the dns cache. If you would like to create a similar script file, follow the steps below:

Step 1 - open a terminal window.

Step 2 - navigate to where you want to save the file. By default, when I open a terminal window I am in my username's directory (/Users/adam). You can change directory up to Desktop if you want to place it on your desktop.

How to enable IPv6 support on a Cisco 3560 switch

If you have tried configuring IPv6 on a Cisco 3560 switch, you may have noticed the ipv6 commands aren't available by default. This often catches me when I am working on a new switch that has never had IPv6 enabled. I just had this happen tonight, so I figured I'd write a brief how-to with some background info thrown in.

Where are the IPv6 commands hiding?

Cisco 3560 switches have a feature called Switch Database Management (SDM) templates. There are various templates that can modify the allocation of system resources to better support different features. What does this mean? By default, a small catalyst switch is built to support 8 routed interfaces and 1024 VLANs. It's not generally used to route OSPFv3 and BGP (though, it can do that). So as a result, the system resources are evenly distributed among the various functions to accommodate a common set of tasks.

CCNA 2013: Now it's Real

If you haven't heard, Cisco has unleashed the new CCNA. Quite a beefy upgrade from the old. I've recorded a quick MicroNugget giving an overview of what's new.

CCNA 2013: All Things New!

All the rumors proved true: Cisco has updated the CCNA yet again (see yellow text in this I post this, the link to the new exam objectives is broken, but I'm sure Cisco will fix it soon).

UPDATE: Cisco has now removed the link. This fellow grabbed a screencap of it. Perhaps they're waiting until 3/26 to announce?

I would consider this one a MAJOR update, once again moving many CCNP topics down into the CCNA program...barrier to entry now sky high! Welcome to the technology world!!

(I'm curious how much more can be added to this entry level certification...)

Service Config - Error opening tftp://

Command Line

If you have worked on a newer Cisco IOS device, you may have seen the following error messages:

%Error opening tftp:// (Socket error)
%Error opening tftp:// (Socket error)
%Error opening tftp:// (Socket error)
%Error opening tftp:// (Socket error)

If you are wondering what these messages mean, it is the result of the config service being enabled by default in some IOS versions. Read on to learn about how it works and how to disable it.

A Focus on CCNA

Based on your feedback, I've created a BUNCH of MicroNuggets (free, fun, fly-by view of some technology). Lately, I've received quite a bit of email on the CCNA I focused a couple MicroNuggets on the top questions I received:

Building a CCNA Home Lab

How to Study for Cisco Exams

Configuring Standard ACLs

Configuring Extended ACLs

Cisco 4500 Series Sup7e Install Notes

One of my projects at work is to replace a couple switches with newer (and larger) 4507R+E with Sup7e. I love projects like this because they're relatively straight forward, but mainly because they are fun! Who doesn't like unboxing a $60,000USD switch and firing it up? It's like a Cisco birthday or something.

Anyway, while configuring this thing, I've noticed a few quirks... idiosyncrasies? "Features"? Whatever you call them, they're new to me and I felt like blogging about it.

SD Memory in a Supervisor

First, just an observation: Cisco now has Secure Digital (SD) memory in a Supervisor. You might be thinking "yeah, I read about that when the Sup7e came out..." However for those who were in the dark, now you know. Here's a picture to share: 

MicroNuggets a Plenty!

CBTNuggets latest idea to love the world and spread the word has been a catalog of FREE MicroNuggets! These are really fun to make, but frankly, I'm out of ideas. I need ideas for Cisco concepts / configurations that I can cover in 5 minutes or so. I've been in Cisco so long that I miss a lot of the basic concepts that are difficult for folks to understand. Anyone have some thoughts or suggestions?

Use the Configure Replace command to speed up your labbing

I've been labbing quite a bit lately, working on Narbik's R&S workbooks, and I've been rebooting my rack after nearly every lab to clear things out. Well, I was perusing the Interwebs and a forum post reminded me of the config replace command. Sheesh! I wish I would have remembered that a few hundred reboots ago...

Even though I knew about this command, and have even included it in a blog post or two in the past, I had forgotten about it since I wasn't using it all that often. So, just in case someone else out there has forgotten about it, I figured I'd do a quick write up demonstrating the command in action and hopefully jostle some memories (or just help me remember if I forget it again).

Here is a 1841 router that used to be R5, but I changed it's hostname to Testing and did a no shutdown on all it's interfaces. Follow the config below for the usage:

Tekcert's 3rd Birthday

Three years ago today, was launched! 2012 was a busy year, both online and offline. I just wanted to write a quick blog post to recognize some milestone and throw a few statistics out there.

I'd like to begin by saying Thank you to all the readers for the support and participation with the forums and comments. It is a pleasure creating a place online that intelligent people can share knowledge and help each other out.

I have received a lot of encouraging messages that have been thankful and kindhearted to keep up with the posting. Many people have shared that they love the blog. I appreciate the kind words and encouragement and will do my best to keep up with the blog posts in between studying for the CCIE Lab exam.

So, that brings us to the stats! Here are some notable numbers for the past year:

Cisco IP Phone Vulnerability Enables Remote Eavesdropping

A recent Cisco Security Advisory details a vulnerability that allows "an arbitrary code execution...that could allow a local attacker to execute code or modify arbitrary memory with elevated privileges." In other words, if you have a Cisco 7900 series IP Phone on your desk, it can be totally pwnd.

This might not come as a surprise to those who have worked with these devices or other IP phones with programmable features. It's basically a little computer with a plastic phone shaped box wrapped around it. If this is a surprise to you or if you don't believe it, check out the video demonstration below.

Unlock your old iPhone


If you happen to have an old iPhone laying around that you no longer use and want to sell or repurpose it, then this bit of information might help you out. You might be asking "what does unlocking an iPhone do?" Good question, unlocking an iPhone (not to be confused with Jailbreaking) lets you use it on other cellular provider networks. For example, if you purchased an iPhone 4 a couple years ago for use with AT&T's network, you would only be able to use it on AT&T's network unless you unlocked it. After unlocking it, you can use that phone on other cellular provider networks that use similar technology as AT&T (GSM), such as T-Mobile.  If you want to use it on a CDMA network, such as Verizon, then you are out of luck as the technologies are different. So, that leaves us with the point of this post: How do you unlock your iPhone?

CCIE Boot Camp Review - Micronics (Narbik's) 12-Day

Studying for your CCIE? If you are, then you might be planning to take a boot camp to help you prepare. A lot of candidates use boot camps to help them prepare and there are many choices available to routing and switching candidates in particular. If you haven’t taken a boot camp yet and are still considering which one to attend or whether or not to attend one at all, then this blog post is written for you.

Save yourself some time with the default interface command

Command Line

If you configure Cisco equipment on a regular basis, you might find yourself in a situation with a large number of router or switch ports that need to be reconfigured. There are several ways you can prep your switch ports to complete your task:

  • You could do a "show run" and then build a script that includes the "no" form in front of each of the old commands, then apply your new script.
  • You could simply overwrite the old config with the new and then go do the no form of the stuff you don't want after the fact.
  • You could erase the startup-config then reload the switch and start from scratch (assuming the device isn't in production anymore).

There are probably another half dozen different ways of simply erasing the config and starting over, but there's one more option that this post is focused on today: the default interface command.

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