Installing Apache+PHP on Ubuntu

Assuming you’re running Ubuntu 11.10 or 12.04 (probably works in others) you can install Apache with PHP like this:
$ sudo su
$ apt-get install apache2 php5 libapache2-mod-php5; service apache2 restart

I’m putting this here for my own reference!

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If you’re going to write an init script, do it properly

“How do I make my Linux process auto-start?” is a fairly common question.  The answer is fairly simple, thank goodness.  Write a shell script, put it in /etc/init.d and run <code>update-rc.d myScriptName defaults</code>.  And you’re done.

Except you’re not, probably.  If you haven’t written your script correctly, you might well hang the boot process.

Init.d and all those rc.d folders are part of the Unix System V init process.  Unlike modern replacement Upstart, init starts processes in series, never in parallel.  If your startup script doesn’t exit, then init won’t either.  If you’re written a really lazy script that doesn’t detatch after starting a process, then you’re screwed 🙂

Another thing to watch our for is how your script is called.  Init will pass either “start” or “stop” to the script depending on what the process should be doing.  If you don’t handle the difference between these (in a case statement, say) and instead just execute the same code whenever the script is run, you’re going to have a really fun time when you try to shutdown or restart your server.  Especially if your script doesn’t detatch and hangs init.  Because then you’re not going to be able to shut down your server cleanly.

It’s been a fun week for my test VMs!

Here’s a little bonus for you.  If you want to start several processes in a specific sequence, you can do this by writing your startup scripts so they don’t exit until each process is ready.  Init allows you to determine the order in which you start processes within a runlevel (that’s what the numbers in the symlink filenames mean) and you know from the above that you can prevent init from processing the next script in it’s queue.  Use this knowledge wisely.

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Running a program as administrator

Windows Vista and Windows 7 have a feature called UAC, which stands for User Account Control. It’s a good idea – programs can’t touch certain files or take certain actions unless you, the user, explicitly grant them administrative privileges. Sounds useful!

To get to the point of this article, as much as UAC is a good idea, it can be very annoying sometimes. Say you want to edit a config file in C:\Program Files\MyApp with Notepad++, your favourite text editor. Normally you’d right click on the file and click “Edit Notepad++” in the context menu. This won’t work in Program Files, though, as it’s a restricted folder. You need to launch Notepad++ with admin rights before you can open your file. (You might be able to read the file without admin rights, but you certainly won’t be able to save your changes!)

Or say you want to do something nifty from the command prompt. In Linux, you’d preface your command with sudo and enter your password when prompted. In Windows, you can’t do that. You need to launch your command prompt with elevated privileges, like so:

That’s: Start -> type “cmd” -> right click -> Run as administrator. Easy.

There’s an obvious downside to this, of course. In Linux you can elevate a single command and then return to being a limited user, all from the same shell. In Windows, though, your command prompt has to be elevated from start to finish. It’s the product of two different cultures. In the Linux world, the command line is king. Everything can be done from it, and it’s usually the best way of doing things. Windows expects you to work with the GUI, though, only dipping into command line mode when you absolutely have to. The GUI has almost everything you need, and you only use the command line for brief periods of time to do obscure things, generally. From that point of view, it makes sense to not have added the ability to elevate commands from within cmd, because you’re not expected to work like that. Completely understandable, but still a shame. Not to mention the source of a lot of nerdrage 😉

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Where have you been, Brian?

It’s been far too long since I last wrote anything here. Let me give you a quick summary of what I’ve been up for the last few months…

Read the rest of this entry »

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