Today I wanted to give my users possibility to test their PHP scripts, but without all the fuss with creating virtual hosts for each one of them. My first and obvious choice was userdir – user creates public_html directory in his home dir, puts there files, and those files are accessible via http://servername/~username/ URL. To enable this behavior you only have to enable userdir module (a2enmod userdir), and remember to set correct permissions to the userdir (chmod +x $HOME) and public_html (chmod 755 $HOME/public_html). I did this, and everything was working fine, except PHP scripts – browser wanted to download them instead of displaying proper processed content. It appeared that apache in Debian has by default PHP disabled for userdirs. To enable scripting in this dirctory, open file /etc/apache2/mods-enabled/php5.conf, find that piece of code:

    <IfModule mod_userdir.c>
        <Directory /home/*/public_html>
            php_admin_value engine Off
        </Directory>
    </IfModule>

and disable it, either by deleting or by commenting it out (precede each line with # sign). You can also change php_admin_value engine setting to On, but if you do that, you will be unable to turn off PHP engine in .htaccess files.

Few days ago I wanted to create VirtualBox image of Debian Squeeze (current testing release). I already had Debian Lenny (stable) image, so the whole process seemed relatively easy – dist-upgrade Lenny, switch to “testing” apt sources, then dist-upgrade. It appeared easy, but in fact there were some bumps on the road. Dist-upgrade broke on “udev” package. From what I’ve understood, udev didn’t want to be upgraded while working with old kernel, and kernel wouldn’t be upgraded because of some unmet dependencies. At first it seemed that the upgrade upgrade process broke down the dependency system and the easiest way was to install the system from scratch. But udev package has an “emergency rope”. When you pull it, you promise udev that before the next reboot you will upgrade kernel – and udev will believe you and install. To use that rope, create an empty file /etc/udev/kernel-upgrade and then manually install the udev package, which already resides in /var/cache/apt/archives directory. After this you can continue dist-upgrade, using -f switch. So the whole set of commands to upgrade the distribution is:

apt-get update
apt-get dist-upgrade
cat > /etc/apt/sources.list << ENDF
deb http://ftp.us.debian.org/debian/ testing main
deb-src http://ftp.us.debian.org/debian/ testing main

deb http://security.debian.org/ testing/updates main contrib
deb-src http://security.debian.org/ testing/updates main contrib
ENDF

apt-get update
apt-get dist-upgrade
touch /etc/udev/kernel-upgrade
dpkg -i  /var/cache/apt/archives/udev_151-3_i386.deb
apt-get dist-upgrade -f

After that upgrade should finish. But be warned – after switching from lenny to squeeze I’ve experienced some problems like kernel not booting (I run previous version and regenerated initrd – it, or something else, helped), problems with VirtualBox guest additions (had to install kernel sources for guest additions to build themselves, then reinstalled virtualbox-ose-dkms package, and then reinstalled guest additions from the CD image attached to VirtualBox).

Upgraded system needs a few touches, but that’s not unusual. Don’t worry about “udevd : SYSFS{}= will be removed in a future udev version, please use ATTR{}= to match the event device” and similar messages while booting – it will be silenced in future versions of some packages. You can fix it if you want by replacing SYSFS with ATTR in /etc/udev/rules.d/* files, but other similar warnings will appear. You can also run upgrade-from-grub-legacy script, if you chose to chainload new grub from the old one during the upgrade. There is also significant amount of files in /var/cache/apt/archives, which can be safely deleted after successful upgrade (in my case it was 2.5GB of data).

Phew, now everything works and I have a proper VirtualBox image of Debian Squeeze.

Recently I’ve upgraded my A/V storage disk from 1TB to 2TB (size of modern HDDs are amazing…), and I had to transfer data from one disk to another in some way. Easiest was of course to simply use cp to copy the whole directory structure. But as USB interface is slow enough, I wanted to employ any possible method to speed things up.

From the old times as a sysadmin I’ve remembered that copying, doesn’t matter local or over the network, was faster if data was copied in chunks – that was true especially when having a lot of small files.

So, to kill two birds with one stone, I employed… tar. Yeah, it’s a very versatile tool – in some time I’ll describe how to use it as a part of a network encrypted backup solution. But here, I used only two instances of tar. You have to remember that if you specify absolute path to the directory you want to transfer, tar will record all elements of the path, only stripping “/” from the beginning. So there are two ways: either record whole path and strip it when “decompressing”, or not to include it at all.

Lets assume that we’re copying data from /media/external0 to /media/external1.

First option:

cd /media/external1
tar cf - /media/external0 | tar x -f - --strip-components=2

Second option:

cd /media/external0
tar cf - * | tar x -C /media/external1 -f -

The first tar command “compresses” the data (either from given directory or from the current one), sends it to the standard output, which goes into the second tar’s input, which decompresses it into the target directory.

To see the progress, you can put cpipe application in the middle like that:

tar cf - /media/external0 | cpipe -vt | tar x -f - --strip-components=2

One note on an improved performance using this method. I didn’t do any benchmarks, but it shouldn’t be worse than a standard cp. tar will be better if the OS is not using any smart pre-buffering. Also I’ve decided to write this entry as an introduction to a future one about over-the-net backup using tar

If you ever wondered if it’s possible to keep screen from blanking/locking while the device is plugged into a charger, the answer is yes, it is possible, without any additional apps. Only the setting for this is strangely placed. To enable this feature, go into Menu → Settings → Applications → Development and tick “Stay Awake”. That’s it.

Recently I’ve started to embrace PowerShell’s great possibilities, and as a result of that, I’ll post some of my “toys”.

On Unix-like operating system I’m using host command to resolve hostnames into IP’s and the other way. On Windows, there’s a nslookup tool, which works just like the Unix equivalent, but to get accustomed to PowerShell, I’ve decided to write a function, which uses internal command to do NS lookups.

Generally, to resolve a hostname you can use this one-liner:

[System.Net.Dns]::GetHostAddresses("devplant.net")

You can shorten it by declaring a short function.

function resolve( [string] $in ){
   [System.Net.Dns]::GetHostAddresses($in)
}

(Defining functions remember not to collide with pre-existing variable names)

But this is only one-way command – to resolve IP address into a hostname, you have to use other command:

[System.Net.Dns]::GetHostbyAddress("72.21.210.250")

To combine both functionalities, you can extend our function, using regular expression to do a naive recognition of IP addresses.

function resolve( [string] $in ){
	if ($in -match "(\d{1,3}\.){3}(\d{1,3})") {
		[System.Net.Dns]::GetHostbyAddress($in)
	} else {
		[System.Net.Dns]::GetHostAddresses($in)
	}
}

Now here’s how you can use it:

PS C:\Users\leafnode> resolve devplant.net

IPAddressToString : 91.192.224.142
Address           : 2397093979
AddressFamily     : InterNetwork
ScopeId           :
IsIPv6Multicast   : False
IsIPv6LinkLocal   : False
IsIPv6SiteLocal   : False

PS C:\Users\leafnode> resolve 72.21.210.250

HostName                Aliases           AddressList
--------                -------           -----------
210-250.amazon.com      {}                {72.21.210.250}

PS C:\Users\leafnode>

You want to try Firefox 3.5 but your favourite extensions are not compatible with the new version? There is a possible solution for this problem.

As in case of extension interface nothing much changed between Firefox 3.0.* and 3.5, it is possible that extension compatible with older version will work without any changes – except the maxVersion setting, which prevents Firefox from installing apparently incompatible extension. Manually, you’d have to download XPI file, decompress, edit settings, re-compress, and install from file. Quite cumbersome, but…

Extension MR Tech Toolkit allows you to tweak some of the extensions’ settings, including maxVersion, without any hassle. Just right-click on an incompatible extension, select “Make compatible” from the menu, and that’s it! After Firefox restarts, if extension really is compatible, it will be working fine.

Windows XP on a netbook works fine with me, but as a person with Linux background it seemed natural to try some distribution on my Wind. As I wanted to try it first, I’ve decided to user some live distribution first. I don’t have an external CD device, but on a previous occasion I’ve managed to cope with bootable USB drives, so it was a natural (and only) choice. I was just about to re-format pendrive I’ve used to boot Linux from, but then I remembered that I have couple of loose 2GB microSD cards I’ve bought just because they were cheap, and an USB card reader. Idea of having an operating system on a so tiny memory card was very appealing!
Continue reading ‘Operating system on a memory card’

If you get error messages like “svn: OPTIONS of ‘http://svn.example.com/svn/module’: could not connect to server (http://svn.example.com)” in Debian Squeeze/testing, you probably have the same problem as I. It appears that recently a broken neon library was transferred to debian/testing repository, what broke subversion client functionality. There are few options.
Continue reading ‘SVN problems in Debian Squeeze/testing’

As I have spent some time resolving the problem, I’ve decided to share the solution with you.

I have bought my MSI Wind as soon as they were available in Poland, in July last year. It was quite some time ago, so I decided to update BIOS. I downloaded it from MSI official page, prepared bootable pendrive using HP USB Storage Disk Format Tool (downloadable from here) and Windows 98 boot files from my own archives (you can find some boot disk images at bootdisk.com). After extracting BIOS files to the pendrive, I’ve booted system from it.
Continue reading ‘MSI Wind system booting problems after BIOS update’

Recently Brian Aker announced that he will develop RDBMS trimmed especially to use with web-apps. It will be named Drizzle.

Features of Drizzle

What will be changed in Drizzle in comparison to MySQL? First of all, whole architecture will be changed. Drizzle will be not monolithic chunk of software like its predecessor, but it will be based on microkernel idea. Most features will be moved from core to optional modules. Those features, like triggers, views, or even query cache, are standard for modern database servers, but are very rarely used in webapps (which is very strange for me, but I’ll come back to this later). One of these modules will be InnoDB engine (owned by Oracle, double licensed), which would make upgrading to newest version of that engine easier. UTF-8 will be standard. Generally – looks nice.

On the other hand, Windows users will be sad, because probably (but not for sure), Drizzle will be available only for Linux and MacOS X. Maybe it’s not such a big deal, because most of production servers are working under non-windows OS’, but for development it would be nice to have a possibility to test-install this RDBMS on Windows.
Continue reading ‘Where are you going, MySQL?’