andunix.net

DynDNS Updates without a Client

andunix — Fri, 04 Jun 2010 18:08:33 +0000

My new hosting provide Strato offers DynDNS. I was searching for a DynDNS client for my OpenSolaris Home Server, but a small bash script does the job as good as any other client.

#! /bin/bash
 
. ${HOME}/.dyndns.cfg
DOMAINS=$(cat ${HOME}/.dyndns.domains)
 
echo "$(date '+%Y-%m-%d %H:%M') $(basename $0)"
for domain in ${DOMAINS}; do
        echo -n "  ${domain} - "
        curl --silent --show-error --insecure --user ${LOGIN} "${UPDATE_URL}?hostname=${domain}"
done

First, the login credentials (the $LOGIN variable) and the server's URL ($UPDATE_URL) are read from the config file ~/.dyndns.cfg.

Here an example config file:

LOGIN="jdoe:secret"
UPDATE_URL="http://members.dyndns.org/nic/update" # DynDNS service
# UPDATE_URL="https://dyndns.strato.com/nic/update" # Strato's DynDNS service

The file .dyndns.domains contains all the domains which should be updated. They must be whitespace separated, I recomment to put one domain per line.

In the for loop, curl is used to update the domains.

Currently, I use the switch --insecure to disable the SSL certificate check. As soon a I found out how to download the server certificate and check it in the correct way I will let you know in an update.

This script is part of my scripts collection, so you can find the latest version at http://bitbucket.org/andunix/scripts/src/tip/bin/cron-dyndns-update.

You can find the DynDNS protocol specification at http://www.dyndns.com/developers/specs/syntax.html.

How To Create a Moveable VM with VirtualBox

andunix — Mon, 17 May 2010 08:55:36 +0000

VirtualBox works good when you use the same VMs all the time. It organizes the disk images in one directory and the configuration files in another. It kees a record of all known disk images and virtual machines.

If you try to carry a VM around with you on an USB stick or want to put it on an encrypted image, then you will get trouble.

First thing is, that you have to be careful when creating the disk image and use the button to select the directory for the disk image or VirtualBox will put it in the default directory.

Second, you don't have an option to specify where to put the VM itself (it's a XML file). It will always be in a subdirectory under the machines directory.

At last, VirtualBox will remember the VM and the associated disk image and complain when they are missing.

To ease the handling of "moveable" VMs, I created a script which creates a VM and a disk image in a given directory and also creates scripts to activate and deactivate the VM.

The Script

So let's have a look at the script. I'll go thought some snippets here, but there is a link to the full script below.

At the top, there are two settings which you may want to change if you use the script. The VBOX= setting contains the full path to VBoxManage, VirtualBox's command line tool. SCRIPT_EXT= is the extensions for the generated scripts.

VBOX="/usr/bin/VBoxManage"
SCRIPT_EXT="command"

Next, there are defaults for the VMs parameters in case the user enters no value.

RAM="512"
DISK_SIZE="8196"
DISK_TYPE="vdi"

The script asks for the parameters and uses the defaults if no value is entered. For example, the question for the disk size:

echo -n "Enter disk size in MiB [${DISK_SIZE}]: "
read a
DISK_SIZE=${a:-${DISK_SIZE}}

The main part. The base directory, the VM and the disk image are created. The VM is configured according to the parameters above.

mkdir -p "${VM_DIR}"
 
${VBOX} -q createvm --name "${VM_NAME}" --basefolder "${BASE_DIR}"
${VBOX} -q registervm "${VM_DIR}/${VM_NAME}.xml"
${VBOX} -q storagectl "${VM_NAME}" --name "IDE Controller" --add ide
${VBOX} -q createhd --filename "${VM_DIR}/${VM_NAME}.vmdk" --size "${DISK_SIZE}" --format VMDK
${VBOX} -q modifyvm "${VM_NAME}" --hda "${VM_DIR}/${VM_NAME}.vmdk"
${VBOX} -q storageattach "${VM_NAME}" --storagectl "IDE Controller" --port 0 --device 1 --type dvddrive --medium emptydrive
 
test ! -z "${RAM}" && ${VBOX} -q modifyvm "${VM_NAME}" --memory "${RAM}"

Finally, the scripts are created. There are three of them: activate, boot (same as activate, just with an additional boot command) and deactivate. The variables are evaluated while creating, so the following code will create the activation script below.

Code:

cat << __SCRIPT__ > "${VM_DIR}/activate.${SCRIPT_EXT}"
#! /bin/sh
 
${VBOX} -q registervm "${VM_DIR}/${VM_NAME}.xml"
${VBOX} -q modifyvm "${VM_NAME}" --hda "${VM_DIR}/${VM_NAME}.vmdk"
${VBOX} -q storageattach "${VM_NAME}" --storagectl "IDE Controller" --port 0 --device 1 --type dvddrive --medium emptydrive
__SCRIPT__

Result:

#! /bin/sh
 
/usr/bin/VBoxManage registervm "/local/temp-vm/temp-vm.xml"
/usr/bin/VBoxManage modifyvm "temp-vm" --hda "/local/temp-vm/temp-vm.vmdk"
/usr/bin/VBoxManage -q storageattach "temp-vm" --storagectl "IDE Controller" --port 0 --device 1 --type dvddrive --medium emptydrive

You can have a look at the code either in the version as of this article or in the latest version. Please keep in mind that not all written here may be true for the later as the script will be improved in the future.

The Future

There are some things, which not yet work as I want them to.

The VM must not have snapshots.
You have to shut down the VM. If you suspend it, it won't detach.
As the DVD drive is removed and recreated, the VM won't remember the mounted image.

If you found this script useful, please let me know (you can use the contact form or leave a comment). You can also subscribe the further blog postings of follow the changes to my scripts collection on bitbucket.org.

Make your Mac feel at Home

andunix — Mon, 03 May 2010 15:24:20 +0000

A small snippet from one of my scripts which tests whether your Mac is in the given (home) WLAN.

#
# Path to 'airport' executeable, as of Mac OS X 10.5.
AIRPORT="/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport"
#
# Set this to your Home WLAN SSID (name):
HOMESSID="mycastle"
#
# Get SSID info from 'airport' and search for $HOMESSID
SSID=$(${AIRPORT} --getinfo | grep ' SSID:')
SSID=$(echo ${SSID} | grep "^SSID: ${HOMESSID}\$")
#
# Branch depending on grep's return code.
if [ "$?" == "0" ]; then
	# in home wlan
	echo "home sweet home..."
else
	# not at home
	echo "on the road again..."
fi

To use this code, set the HOMESSID to your SSID (the name of the wireless network) and replace the two echo lines with your code.

Set PHP Variables in .htaccess Files

andunix — Thu, 29 Apr 2010 15:07:43 +0000

If your PHP scripts run longer than the maximum execution time set by your webhoster, then you will see a message like this:

Fatal error: Maximum execution time of 30 seconds exceeded in ...

To override the default for your webspace, you can use the php_value directive in a .htaccess file.

To set the value to "0", which means no limit, add this line:

php_value max_execution_time 0

I suggest to either set it to unlimited, run the long running script and then comment it out or set it to some reasonable value like 120 or 300, depending on the time the script usually needs.

Memory Usage of a Solaris Container (Zone)

andunix — Wed, 21 Apr 2010 09:17:09 +0000

Last week one of my servers ran out of RAM and Swap. Shame on me for not monitoring that, but it's now.

As the server is running several zones, my first question was: Which zone is eating up my RAM? So, here are the commands I used.

Part 1: Find the Zone

To see the memory usage of the running zones:

prstat -Z

From the prstat(1M) man page:

-Z Report information about processes and zones. In this mode, prstat displays separate reports about processes and zones at the same time.

Part 2: Find the Process(es) in the Zone

To see which processes use the most RAM in the zone, use one of these commands:

prstat -z zone -s rss
prstat -z zone -s size

From the prstat(1M) man page:

-z zoneidlist Report only processes or LWPs whose zone ID is in the given list. Each zone ID can be specified as either a zone name or a numerical zone ID. See zones(5).
-s key Sort output lines (that is, processes, lwps, or users) by key in descending order. Only one key can be used as an argument.
- rss Sort by resident set size.
- size Sort by size of process image.

Note the upper case -Z in the first an the lower case -z in the second command.

For more information about prstat, see the manual prstat(1M).

Drupal: Reverse Proxy

andunix — Tue, 16 Mar 2010 17:00:34 +0000

skybow wrote the very helpful article "Drupal via HTTPS/SSL Proxy Server (shared certificates)".
While following his advice, I found some improvements.

To reduce the amount of editing and to increate the reusability, I substituted www.example.com with $_SERVER['SERVER_NAME'] and ssl.proxy.org with $_SERVER['HTTP_X_FORWARDED_HOST'].

Additionally, I added the line ini_set('session.cookie_path', '/'.$_SERVER['SERVER_NAME'].'/'); to limit the cookies to the path, which is associated with the host.

That the cookie will bei set for the path /andunix.net/ insted of the root of the reverse proxy.

This improves security, as other hosts, using the same reverse proxy, won't see the cookie and also enables mutliple logins, if using multiple domain names for one installation.

It has also a nice side effect: I separated my normal editor account from the admin account, so that my normal account has not all the rights.
If I want to log in with both accounts at the same time, I can do this using different domains.

$request_type = ($_SERVER['HTTP_X_FORWARDED_HOST'] == 'ssl.webpack.de') ? 'SSL' : 'NONSSL';
if ($request_type != "SSL"){
  $base_url = 'http://' . $_SERVER['SERVER_NAME'];  // NO trailing slash!
  $cookie_domain = $_SERVER['SERVER_NAME'];
} else {
  $base_url = 'https://' . $_SERVER['HTTP_X_FORWARDED_HOST'] . '/' . $_SERVER['SERVER_NAME'];  // NO trailing slash!
  $cookie_domain = $_SERVER['HTTP_X_FORWARDED_HOST'];
  ini_set('session.cookie_path', '/'.$_SERVER['SERVER_NAME'].'/');
  $_SERVER['HTTPS'] = 'on';
  $_SERVER['REQUEST_URI'] = '/' . $_SERVER['SERVER_NAME'] . $_SERVER['REQUEST_URI'];
  $conf = array(
    'reverse_proxy' => TRUE,
    'reverse_proxy_addresses' => array($_SERVER['REMOTE_ADDR']),
  );
}

Home Server Goals

andunix — Tue, 02 Mar 2010 15:41:41 +0000

As Constantin suggested, here is a list of services, which my home server should provide:

Personal Video Recorder: I'm using the EyeTV Hard- and Software from Elgato to record, cut and archive TV broadcasts.
Secure File Archive / Backup: I want my digital camera photos and other precious files to be stored at serveral places and to be protected with checksums.
A/V Media Server: I want to store my MP3 files and the videos from the above PVR to be stored an be served to clients in the local LAN but not to the Internet.
Web Hosting: I want to run web application at home. Usually, I'm hosting my webapps at Host Europe, but there are some apps which I can't or don't want to host there. This includes PHP and JEE applications with MySQL as database.
LAN Gateway: I want to sercurely log into the LAN via SSH and transfer files from and to the server.
I had also a "OpenSolaris Sandbox" on this list, but I think that one is served bettes as a VirtualBox on my Laptop than on my home server.
to be continued...: There will be more requirements in the future, like hosting my own Jabber server.

The server will continue to run Mac OS X and OpenSolaris, as the first goal on the above list requires Mac OS X and I haven't found an acceptable PVR solution for OpenSolaris yet. This is currently done using an Mac mini with Mac OS X and running an virtualized OpenSolaris on top of it. In the future, there may be two distinct servers due to some limitations of this constellation (e.g. having to stop the OpenSolaris server to install Mac OS X patches).

Hello Drupal

andunix — Sun, 28 Feb 2010 23:00:00 +0000

Some time ago, I decided to migrate my blog from DokuWiki to Drupal. Blogging with DokuWiki was OK using the plugins from the DokuWiki Blogsuite BundleHub, but Drupal has some advantages.

It's always fascinating to get into a new technology. After using misc. wiki systems and Wordpress, I wanted to try a content management system. I had a quick look into Drupal, Joomla and Silverstripe, and then decided to go with Drupal.

One very interesting part of Drupal is the Content Construction Kit (CCK). This was also the main reason to choose Drupal. I've already set up my Projects a special content nodes and thinking about doing the same for tasks and bookmarks.

The power of the CCK shows in the Blogroll channel in the sidebar. I set up a "Friend" content type and gave it attributes like blog URL and Twitter name. The Views module rendes the list of friends as a nice list in the sidebar. The credits for this solution go to Constantin Gonzalez which implemented this cool feature on his blog first.

ReLAX

andunix — Fri, 27 Nov 2009 16:36:00 +0000

Thanks to Wolfgang Stief and Constantin Gonzalez, I got hold on one of the proceedings of the Linux Kongress and OpenSolaris Developer Conference.
In this book, I found amoung other, also very interesting, articles one about LAX by Thomas Groß.

LAX has some very interesiting concepts, but, unfortunately, it doesn't fit my needs.
So I decided to take some of the concepts of LAX and build my own sysadmin-automation-framework.

In lack of a good project name, I named it "ReLAX".

To get startet, here is a small comparison of the concepts of LAX and ReLAX:

The most fascinating idea is the building of an API with shell-scripts. I adopted this from LAX.
LAX uses an LDAP server to store the configuration. I decided to allow any server which can be read by ''curl'', ''wget'' or ''cat''. This allows http, https, ftp, ftps and file URLs.

That's it for now, stay tuned...

I started documenting the API, so you might want to have a look there..

Found Geocache GC1VY11 "Ringpromenade"

andunix — Mon, 26 Oct 2009 11:36:00 +0000

Yesterday, I visited my first geocache.
For those interested, here is evidence: