What is Android doing when it says “optimizing apps” after a system upgrade?

Android FAQ: What is Android doing when it says “optimizing apps” after an Android system upgrade (and reboot)?

The short story is that Android is doing what it says, creating an optimized version of each app for the new version of Android you just upgraded to. This process makes each app start as fast as possible with the new Android version.

How to restart Mac OS X networking from the command line

I've been having a problem with my MacBook Air (running Mac OS X Lion) and my wireless router, so today I decided to write a script to restart the OS X wireless networking service from the command line. In short, I use this OS X command to turn off the Mac networking service:

sudo ifconfig en0 down

and I use this command to turn the Mac wireless network service back on:

sudo ifconfig en0 up

(I found these commands on the website I linked to.)

How to gracefully restart Nginx

Nginx FAQ: How do I gracefully restart Nginx?

On a Unix or Linux system, you can restart Nginx without having to manually stop it and start it by sending a HUP signal (a "hangup" signal) to the main Nginx process. So, if the process id happened to be 1234, you would issue this command:

kill -HUP 1234

The easy way to get the actual Nginx process id is by looking at the, which is kept in the Nginx log directory by default. On my server, the file is located here:

iptables restart tip - How to make your Linux iptables firewall automatically restart after a reboot

iptables restart FAQ: How do I make my iptables firewall start/restart after I reboot my Linux system?

I was going to write a tutorial about configuring a firewall on a Linux system using iptables, but then I found this great CentOS iptables tutorial, and I think they really nailed it.

The only thing I think they didn't fully cover is how you get your Linux iptables firewall to start up again properly after your Linux system is rebooted (which is kind of a huge deal). To that end, I thought I'd describe the process of getting your iptables firewall to restart after a system reboot.

And -- as an added bonus -- this same process will help you get any Linux service to automatically start after a reboot.

iPhone "Slide for Emergency" and "Activated" error messages

I'm not sure what I keep doing, but every once in a while when I turn on my iPhone 3G (after turning it off completely, i.e., a restart/reboot) I see a couple of different weird "error" messages. The first error message says, "Slide for emergency", and looks like this:

A Tomcat startup script that deletes old log files before starting up

One thing I don't like about using Tomcat in development and test environments is that the log files tend to grow, eventually growing for days on end if you don't clean them out. Having all these old log files hanging around just makes it harder to debug development problems, so I like to delete them all every time I restart Tomcat.

Deploy only your JSP files with this Ant build task

A lot of times when you're working on a Java web application you only need to deploy your JSP files. This happens, for instance, when you're just editing the JSP files to modify the look and feel of your web application. In cases like this there's no need to rebuild your entire application, deploy it, then restart your application server (Tomcat, Glassfish, JBoss, whatever).

My Windows Ant/Tomcat web application build process

I don't like the off-the-shelf process of developing web applications with Ant and Tomcat on Windows computers. Rather than get into my angst, here's the way I think the Ant build process should work with Tomcat:

How to restart/reboot an iPhone or iPod

iPhone reboot FAQ: How do I restart (reboot) an iPhone, iPod, or iPad?

As a new iPhone user, after hearing that the iPhone may suffer from a memory leak which causes applications to become slower over time, I looked at my phone and wondered "How do I turn off my iPhone?", quickly followed by "How do I restart my iPhone?"