Tag: Linux

Logitech Media Server vs Ubuntu 12.04

JonTheNiceGuy Leave a comment

A while back I upgraded my home server to Ubuntu 12.04 (while it was still in beta) and immediately the first thing I noticed was that the Logitech Media Server (previously known as Squeezebox Server) had stopped working.

Checking through the logs, I saw a lot of messages about perl dependencies being missing or not working [1]. As I was a bit busy at the time (the decision to upgrade had been due to something else entirely), I put it to one side (much to my wife’s annoyance!) to pick up later.

As I’ve been wallowing at home the past couple of days with a stomach bug, and not really been fit to do much other than moan, lie there and feel sorry about myself, I thought about what I could do to get my squeezebox server back up and running.

A few Google searches later, and I turn up this page: http://forums.slimdevices.com/archive/index.php/t-89057.html which suggests that this message below is due to Ampache… which now that I look at the log entry, it kinda makes sense. Queue digging into the depths of the server.

Under Ubuntu, all the serious configuration for the server is stored in /var/lib/squeezeboxserver, which includes the plugins.

So, firstly, I deleted the downloaded Zip file from /var/lib/squeezeboxserver/cache/DownloadedPlugins/Ampache.zip

rm /var/lib/squeezeboxserver/cache/DownloadedPlugins/Ampache.zip

Next, I removed the unpacked plugin from /var/lib/squeezeboxserver/cache/InstalledPlugins/Ampache

rm -Rf /var/lib/squeezeboxserver/cache/InstalledPlugins/Ampache

I made a mistake here on my box, and restarted the server. Woohoo it came back up, but the first thing it did was to re-download the plugin again! D’oh. So, now I need to find what’s telling it to re-install the plugin. Queue a quick grep. Ahhh, there’s a file called extensions.prefs, which says:

prefs/plugin/extensions.prefs:  Ampache: 1

And another file called state.prefs which says:

prefs/plugin/state.prefs:Ampache: needs-install

Note, these are both the output from grep – so the filename includes the path from the point /var/lib/squeezeboxserver. A quick nano away (or whatever editor you prefer) and I’d removed the line from the extensions.prefs which showed Ampache: 1, but the state.prefs was marginally more tricky. In here it lists them in three states, enabled, disabled and needs-install. So, I changed it to show disabled and then restarted the service. Tada. I’ve got a working Logitech Media Server again! Huzzah!

[1] Log file looks like this:

Slim::bootstrap::tryModuleLoad (285) Warning: Module [Plugins::GrabPlaylist::Plugin] failed to load:
Can't locate Math/VecStat.pm in @INC (@INC contains: /usr/sbin/Plugins/Gallery /var/lib/squeezeboxserver/cache/InstalledPlugins/Plugins/Gallery /var/lib/squeezeboxserver/cache/Installed
Plugins/Plugins/CustomScan/lib /var/lib/squeezeboxserver/cache/InstalledPlugins/Plugins/Ampache/lib CODE(0xb911c40) /var/lib/squeezeboxserver/cache/InstalledPlugins /usr/share/squeezebo
xserver/CPAN/arch/5.14/i386-linux-thread-multi-64int /usr/share/squeezeboxserver/CPAN/arch/5.14/i386-linux-thread-multi-64int/auto /usr/share/squeezeboxserver/CPAN/arch/5.14.2/i686-linu
x-gnu-thread-multi-64int /usr/share/squeezeboxserver/CPAN/arch/5.14.2/i686-linux-gnu-thread-multi-64int/auto /usr/share/squeezeboxserver/CPAN/arch/5.14/i686-linux-gnu-thread-multi-64int
 /usr/share/squeezeboxserver/CPAN/arch/5.14/i686-linux-gnu-thread-multi-64int/auto /usr/share/squeezeboxserver/CPAN/arch/i686-linux-gnu-thread-multi-64int /usr/share/squeezeboxserver/li
b /usr/share/squeezeboxserver/CPAN /usr/share/squeezeboxserver /usr/sbin /etc/perl /usr/local/lib/perl/5.14.2 /usr/local/share/perl/5.14.2 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/
5.14 /usr/share/perl/5.14 /usr/local/lib/site_perl . CODE(0xb911e20)) at Slim/Player/Player.pm line 18.
BEGIN failed--compilation aborted at Slim/Player/Player.pm line 18.
Compilation failed in require at /var/lib/squeezeboxserver/cache/InstalledPlugins/Plugins/GrabPlaylist/Plugin.pm line 22.
BEGIN failed--compilation aborted at /var/lib/squeezeboxserver/cache/InstalledPlugins/Plugins/GrabPlaylist/Plugin.pm line 22.
Compilation failed in require at (eval 924) line 2.
BEGIN failed--compilation aborted at (eval 924) line 2.

Nice, right?

Trials and Tribulations of StatusNet with Meteor

JonTheNiceGuy 6 Comments

I have recently moved this domain to a VPS, and the main reason was so I could speed up my StatusNet site, but a nice side effect to that was that I could add the auto-content-update plugins to my StatusNet site.

I plumped for Meteor, as it was more-or-less the defacto choice (or so it seems at the moment), and went away to follow the instructions at http://meteorserver.org. Having added my meteor server, and knowing that there’s only me that is likely to be using the auto-update plugin, I set up Apache to proxy the meteor connections.

Here’s what I’ve got:

I used the default /etc/meteord.conf, but added at the top of the file the following two lines:

SubscriberIP 127.0.0.1
ControllerIP 127.0.0.1

I started meteor and checked that meteor was running:

# netstat -an | grep 467
tcp        0      0 127.0.0.1:4670          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:4671          0.0.0.0:*               LISTEN

Next, I added a new file to /etc/apache2/sites-available called metor-proxy

<VirtualHost *:80>
        ServerAdmin webmaster@localhost
        ServerName meteor.jon.sprig.gs

        ErrorLog ${APACHE_LOG_DIR}/meteor-error.log

        # Possible values include: debug, info, notice, warn, error, crit,
        # alert, emerg.
        LogLevel warn

        CustomLog ${APACHE_LOG_DIR}/meteor-access.log combined

        ProxyPass / http://127.0.0.1:4670/
        ProxyPassReverse / http://127.0.0.1:4670/
</VirtualHost>

Then, I used the a2ensite script:

# a2ensite meteord-proxy
Enabling site meteord-proxy.
Run '/etc/init.d/apache2 reload' to activate new configuration!

I ensured my DNS had an entry for this hostname, it does.

Lastly, I added some lines to my StatusNet config.php file:

addPlugin('Meteor', array(
    'webserver' => 'meteor.jon.sprig.gs',
    'webport' => 80,
    'channelbase' => 'statusnet',
    'controlserver' => '127.0.0.1',
    'controlport' => '4671'
));
addPlugin('Realtime');

All looks good so far, right?

I fire up my StatusNet site, and check in firebug – the meteor.js file is being loaded OK, but straight away, it’s loading /poll.html, and not /stream.html, so I’m guessing there’s an issue here…

Head over to the console tab, and what do we see here?

Permission denied to access property 'Meteor'
parent.Meteor.register(this);

AAARRRGGGGHHH!

I’ve fallen foul of the XSS that we were trying to prevent.

But, hang on a second. Perhaps this is because we’ve configured StatusNet to use HTTPS always. ARGH.

Let’s put the proxy lines into the SSL config for apache (inside the VirtualHost *:443 section):

        ProxyPass /poll.html http://127.0.0.1:4670/poll.html
        ProxyPassReverse /poll.html http://127.0.0.1:4670/poll.html
        ProxyPass /stream.html http://127.0.0.1:4670/stream.html
        ProxyPassReverse /stream.html http://127.0.0.1:4670/stream.html
        ProxyPass /meteor.js http://127.0.0.1:4670/meteor.js
        ProxyPassReverse /meteor.js http://127.0.0.1:4670/meteor.js
        ProxyPass /push/ http://127.0.0.1:4670/push/
        ProxyPassReverse /push/ http://127.0.0.1:4670/push/

Edit the meteor.js file (from /usr/local/meteor/public_html/meteor.js) and changing all http:// to https:// and port==80 to port=443, then amending the StatusNet’s config.php to show:

addPlugin('Meteor', array(
    'webserver' => 'jon.sprig.gs',
    'webport' => 443,
    'channelbase' => 'statusnet',
    'controlserver' => '127.0.0.1',
    'controlport' => '4671',
    'protocol' => 'https'
));

OK, that’s looking a lot healthier. Oh, no it isn’t – now, my poll.html requests are going to http://jon.sprig.gs:443/poll.html ARGH.

I’m very confused now.

I’ve commented out the Meteor and realtime plugins while I try to figure it all out :(

Installing MOTP-AS under Ubuntu 11.10

JonTheNiceGuy 3 Comments

Please note, I am having issues with localhost authentication. See below

MOTP-AS is a simple installable two-factor authentication system using the mOTP algorythm for generating one-time passwords. MOTP-AS integrates with FreeRadius to provide the same authentication to log in to managed servers in a consistent manner.

I’ve recently installed this on my Ubuntu 11.10 laptop and on my Ubuntu 12.04 Beta server, and the installation instructions worked on both, so I thought I’d share them with you.

Installing appropriate packages

sudo apt-get install libpam-radius-auth freeradius mysql-server phpmyadmin

Alternatively, use tasksel to install the LAMP server task, then

sudo apt-get install libpam-radius-auth freeradius

Download the latest version of motp-as from http://motp-as.network-cube.de/index.php/download/current-version

Unpack it.

tar xfz ~/Downloads/motp-as*

Setting up the database

Go into the Setup/MySQL directory of the MOTP-AS directory. Edit motp_schema.sql at the line “CREATE USER”. Change the password from motp to something more secure.

mysql -u root -p < motp_schema.sql

Now update Setup/config.php with the new password you just created.

Setting up the web site

Copy the HTML directory to /var/www/motp (or somewhere else in your web root). You may need to do this either as root, or as a user with permissions to write to /var/www

cp -Rf ~/MOTP-AS_*/HTML /var/www/motp

Note this must be done after you’ve made your changes to Setup/config.php

Setting up FreeRadius

Stop the FreeRadius service

sudo /etc/init.d/freeradius stop

Users

Backup the users file

sudo mv /etc/freeradius/users /etc/freeradius/users.dist

Edit the users file you’re about to copy in

nano ~/MOTP-AS_*/Setup/Freeradius/users

Find the part where it says “/var/www/htdocs/radius-auth.php” and change that to “/var/www/motp/radius-auth.php”

Copy in the new users file

sudo cp ~/MOTP-AS_*/Setup/Freeradius/users /etc/freeradius/users

Dynamic Clients

Backup the dynamic-clients file

sudo mv /etc/freeradius/sites-available/dynamic-clients /etc/freeradius/sites-available/dynamic-clients.dist

Edit the new dynamic-clients file

nano ~/MOTP-AS_*/Setup/Freeradius/dynamic-clients

Find the three lines saying “/var/www/htdocs” and replace that string with “/var/www/motp” (I use Ctrl+W, Ctrl+R in nano to do a replace-all.)

Copy in the new dynamic-clients file

sudo cp ~/MOTP-AS_*/Setup/Freeradius/dynamic-clients /etc/freeradius/sites-available/dynamic-clients

Then make that function available

sudo ln -s /etc/freeradius/sites-available/dynamic-clients /etc/freeradius/sites-enabled/dynamic-clients

Accounting

Amend the default script to enable accounting

sudo cp /etc/freeradius/sites-available/default /etc/freeradius/sites-available/default.dist

Then edit it to use the MOTP accounting functions

sudo nano /etc/freeradius/sites-available/default

Search for the line “accounting {” then comment that whole block out with the hash/pound sign “#“. Fortunately in the distribution supplied default file, this only means commenting out a few lines, which are “detail“, “unix“, “radutmp“, “exec“, “attr_filter.accounting_response“, and then the closing “}” for that block.

If you’re using nano, press the insert key (or Ctrl+R if you can’t find that easily) and enter /home/MyUserName/MOTP-AS_v0.7.2/Setup/Freeradius/accounting (amend the path as appropriate). Replace the section “/var/www/htdocs” with “/var/www/motp“.

Save and exit

Finishing off FreeRadius

sudo /etc/init.d/freeradius start

Install your client

Personally, I have an Android device, and I chose to install the Mobile-OTP app from the Android Marketplace. I also, through work, have a Nokia 6303i Classic, on which I installed the MOTP application from the MOTP site.

I’ve heard good things about iOTP for iPhone, although I personally don’t have one.

Configuring MOTP

Go to http://localhost/motp (or https://yourdomain.com/motp)

Login with the username admin and password of motp.

Securing the admin account

Click on the red text in “First time configuration”

Click on “Change password of User ‘admin’”

Enter a new password. Do not set the time or uses section of this page. Click “Set“. Ignore the warning.

Click on “Home”

Setting up your first user

Click on “Quick Add” (under “Wizards”)

Enter a username. It should be the username for your Ubuntu 11.10 device.

On the client, create a profile for the device. Most of them create a profile by asking for a seed, rather than a secret, so those will likely be more than 16 characters long – maybe even 20 (Mobile-OTP for Android) or 25 (MOTP Java app).

Once you’ve got your secret (on Mobile-OTP, by pushing-and-holding on the profile name and selecting “Show Secret“, on MOTP Java app, once you’ve put 0000 as the PIN for the first time to initialize it, you get a string “Init-Secret:“), put that into the “Secret” field, and then ask the user to set their pin here – I suggest 1234 initially, as the user can change it to something they want after.

Click OK, then click “Logout” and test authentication. If it all goes OK, they should be presented with “Welcome to the Mobile OTP Authentication Server“.

Under “Settings” they can change their own PIN.

Testing radius authentication works OK

Run the radius testing program, like this, as a user:

radtest username passcode localhost 0 testing123

(This assumes the default localhost password hasn’t changed)

If you get anything like “rad_recv: Access-Reject packet from host“, then you’ve failed to configure something properly, or you’ve entered the PIN or code wrong.

Restart FreeRadius in debugging mode by doing the following:

/etc/init.d/freeradius stop
/usr/sbin/freeradius -X

This will produce a large quantity of logs on-screen, so I’d suggest running the test itself from a separate window. Run the radtest command (listed above) again. Look for your error messages. In my case, I forgot to update the line in users, so I saw this error message: Could not open input file: /var/www/htdocs/radius-auth.php

To find where this fault was, I did (as root, in /etc/freeradius)

find -R 'htdocs' /etc/freeradius

And got back: users: Exec-Program-Wait = “/usr/bin/php /var/www/htdocs/radius-auth.php %{User-Name} %{User-Password} %{Client-Shortname}”

That told me the fault was in the users file.

Fix the issue, check it again, and when you get this message “rad_recv: Access-Accept packet from host” press Ctrl+C to cancel the test mode of FreeRadius, and then run:

sudo /etc/init.d/freeradius start

Configuring pam_radius_auth.conf

Edit /etc/pam_radius_auth.conf

sudo nano /etc/pam_radius_auth.conf

Find the line which says “127.0.0.1” and replace the shared secret with something you want your server to use. You will also need to amend /etc/freeradius/clients.conf and replace the “secret” in the localhost client there (by default, it’s “testing123” in freeradius).

If you want to use your OTP for all authentication credentials, edit /etc/pam.d/common-auth, or if you just want to use it with specific access protocols, edit the relevant file in /etc/pam.d for the authentication systems you want to use OTP for.

You need to add the following line – either on the line before “@include common-auth” (for non common-auth files) or after the primary comment block for common-auth.

auth sufficient pam_radius_auth.so

Open a separate terminal session to your box (especially! if you’re remote) and ensure you can still login with your regular credentials.

Then try a connection with your radius credentials. It should just work! If not, stop the freeradius server and re-run it using /usr/sbin/freeradius -X and see whether you’re getting a different error message.

** UPDATE **

I have noticed that I’m getting locked out when using my non-radius credentials. This is probably due to the placement of the line in the /etc/pam.d/common-auth – it should probably come after the pam_unix.so line, but I’ve not tested that yet. I’m also going to try to suggest that there be an optional time-out period on locked accounts to the developers of MOTP-AS.

The second issue I’m struggling with is that I’m getting errors when using the LightDM. I’m getting the following error message in /var/log/auth.log:

pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "spriggsj"

I don’t know if this is because I’m using ecryptfs as well, or because there’s something wonky going on with the common-auth structure I’m using.

Using Amazon an EC2 instance as an off-site CronJob

JonTheNiceGuy Leave a comment

I run the CCHits.net website, and part of the day-to-day tasks that running the site entailed was the daily show creation which involved creating some text-to-speech audio for insertion into the podcasts. As I run the website on shared hosting, to which I didn’t have full access to the OS, I couldn’t just install Festival on the platform, and for whatever reason (I never did figure out what went wrong), I couldn’t build Festival to run on the shared host either.

Until “The Big Rewrite” (the capitals are totally worth it), I’d been doing the text-to-speech on my home server, but frankly, I’m on DSL, which meant I needed to set up Dynamic DNS, I had to be sure the server was always up (and it wasn’t!), etc, etc, etc. While I was looking into why I couldn’t get Festival to build, someone said “Well, why not just use EC2 to do it”.

After nearly a year of faffing about trying to make the …….. stupid thing work (as is testified by the draft in this very blog called “How I built my Audio Stack for CCHits”), I finally decided to spin up an EC2 instance for just this one task.

Now, I’m not the greenest guy on the block – hell, I drive 45 minutes into work each day, but I figured, why keep an EC2 instance running all the time, when I only need it for less than 20 minutes each day, so I did some reading, and found a post on making EC2 do the hard work for you, using the scalable computing APIs, but frankly, all I actually needed was the code to make it spin up, run the task and shut down again, especially as with using his methods, I’d have needed to either create an AMI image, or download the festival voice files each time… at around 100Mb. Not good. I ended up using the stuff I did know (bash scripting, cron tasks) and ditching the stuff I didn’t (AMI files, scalable computing API). I may revisit this later to do it the way he said instead. We’ll see :)

So, here’s the crack.

Create your EC2 image. It doesn’t need to do anything fancy yet – just boot up and keep running. You’ll do some tweaks later. Make a note of the instance number – it’ll probably start i- and then 8 or so hexedecimal digits, like this: i-12345678.

On your shared web host, download the EC2 API tools. According to this page, the API tools are available from here. The first link of those two is unlikely to change for a while, the second, maybe more so. You’ll need to make sure you have Java installed on that web host.

Once you’ve got the tools, you’ll need to create an X.509 certificate and key pair. See this page to find instructions. It was pretty straightforward.

So, you now have in, let’s say for sake of argument, your home directory:

  • /home/user/ec2-api-tools-x.x.x.x # The directory containing all the EC2 API tools
  • /home/user/ec2-keys/pk-{32[A-Za-z1-0]}.pem
  • /home/user/ec2-keys/cert-{32[A-Za-z1-0]}.pem

Also, you have java in /usr/bin/java.

Create the following script also in /home/user/ec2-api-tools-x.x.x.x – I called it ec2-wrapper.

#!/bin/bash
export EC2_HOME=/home/user/ec2-api-tools-x.x.x.x
export JAVA_HOME=/usr
export EC2_KEY=/home/user/ec2-keys/pk-{32[A-Za-z1-0]}.pem
export EC2_CERT=/home/user/ec2-keys/cert-{32[A-Za-z1-0]}.pem
${EC2_HOME}/bin/$* -K ${EC2_KEY} -C ${EC2_CERT

Obviously, you should change your paths to match what you have. What this script does is to add the X.509 certs to every EC2 request, plus adds the appropriate java and EC2_HOME paths to the script before running it.

I set up a CRON job (using crontab -e) to schedule the regular startup of the instance. Here’s the entry from my crontab:

#M   H  DoM Mth DoW  Command (Regular Crontab columns)
30   1   *   *   *   /home/user/ec2-api-tools-x.x.x.x/ec2-wrapper ec2-start-instances i-12345678
30   2   *   *   *   /home/user/ec2-api-tools-x.x.x.x/ec2-wrapper ec2-stop-instances i-12345678

So, this runs the start task at 30 minutes past 1am, local server time, and the stop task at 30 minutes past 2am. The second one there is just to be on the safe side, as we’ll try to shut down the box once it’s finished processing anyway. This way, the maximum time you’ll be billed for is 1 hour of time each day.

I then logged into my EC2 machine, and created, then tweaked the script from the earlier blog post (the scalable computing one).

#!/bin/bash -x
exec > >(tee /var/log/user-data.log|logger -t user-data -s 2>/dev/console) 2>&1
#
# This code is licensed under an Apache License - for the original 
# code and license, please see the footer of this script.
#
# !!!IMPORTANT!!!
# Edit this file and change this next line to your own email address:
#

EMAIL=user@example.com

# Get some information about the running instance
instance_id=$(wget -qO- instance-data/latest/meta-data/instance-id)
public_hostname=$(wget -qO- instance-data/latest/meta-data/public-hostname)

# Wait 5 minutes in case we want to get in to stop this from doing stuff
Sleep 300

if [ -f /home/ubuntu/donotrun ]
then
  exit 0
fi

# Send status email
/usr/sbin/sendmail -oi -t -f $EMAIL <<EOM
From: $EMAIL
To: $EMAIL
Subject: Running EC2 Scripts

== Making sure everything is up to date ==

`cd /home/ubuntu/website-rewrite && su -c "git pull" ubuntu 2>&1`

== Running the scheduled task ==

`php /home/ubuntu/website-rewrite/scheduled_task.php`

== Notes ==

This email was generated on the EC2 instance: $instance_id

If the instance is still running, you can monitor the output of this
job using a command like:

  ssh ubuntu@$public_hostname tail -1000f /var/log/user-data.log

EOM

# Give the email some time to be queued and delivered
sleep 300 # 5 minutes

if [ -f /home/ubuntu/shutdownwhendone ]
then
  shutdown -h now
fi

exit 0

########################################################################
# For more information about the original version of this code see:
#   http://alestic.com/2011/11/ec2-schedule-instance
# The original code and its license are available on github:
#   https://github.com/alestic/demo-ec2-schedule-instance
########################################################################

So, with that, I get a script which runs on schedule, on an EC2 platform, I get a confirmation e-mail it’s running. It shuts itself down, and hopefully, keeps on trucking :)

Transfer my files using SFTP and SCP only?

JonTheNiceGuy Leave a comment

A colleague today asked for some guidance around setting up an SFTP and SCP only account on a RedHat based Linux machine.

I sent him a collection of links, including one to the CopSSH project, and he implemented the code on that link, but then struggled when it didn’t work.

Aside from the fact the shell wasn’t copied into /etc/shells (which wasn’t disastrous, but did mean we couldn’t reuse it again later), it was still returning an error on each load.

Doing some digging into it, and running some debugging, I noticed that pscp (the PuTTY SCP) tool uses the SFTP subsystem rather than the SCP command to upload files, so we need to also check that the SFTP server hasn’t been called, instead of the SCP command, and also the SCP command needs to be corrected.

Here follows a script, complete with comments. Personally, I’d save this in /bin/sftponly, created and owned by root, and set to permissions 755 (rwxr-xr-x). Then, set the shell to this for each user which needs to do SFTP or SCP only.

#!/bin/bash
# Based on code from http://www.itefix.no/i2/node/12366
# Amended by Jon Spriggs (jon@sprig.gs)
# Last update at 2011-09-16

# Push the whole received command into a variable
tests=`echo $*`

# Set up a state handler as false
isvalid=0

# Test for the SFTP handler.
# The 0:36 values are the start character and length of the handler string.
if [ "${tests:0:36}" == "-c /usr/libexec/openssh/sftp-server" ]; then
  # Set the state handler to true
  isvalid=1
  # Configure the handling service
  use=/usr/libexec/openssh/sftp-server
fi

# Test for the SCP handler.
if [ "${tests:0:6}" == "-c scp" ]; then
  # Set the state handler to true
  isvalid=1
  # Configure the handling service
  use=/usr/bin/scp
fi

# If the state handler is set to false (0), exit with an error message.
if [ "$isvalid" == "0" ]; then
  echo "SCP only!"
  exit 1
fi

# Run the handler
exec $use $*

Quick Fix for Apache CVE-2011-3192 – Ubuntu/Debian

JonTheNiceGuy 2 Comments

Please note – Apache have released a fix to this issue, and as such the below guidance has now been superseded by their fix.

I have been aware of the Apache web server issue for the last few days, where an overly wide range is requested from the server, leading to a crash in the server. As a patch hasn’t yet been released by Apache, people are coding their own solutions, and one such solution was found at edwiget.name.

That fix was for CentOS based Linux distributions, so this re-write covers how to do the same fix under Debian based distributions.
Read More

VNC in Ubuntu 11.04 with Unity

JonTheNiceGuy Leave a comment

I recently bought myself a new laptop. Sometimes though, I want to check something on it on a rare occasion when I’ve not taken it with me. In comes VNC. Under Ubuntu 11.04, turning on VNC support is pretty straight forward.

To turn on VNC, go to the power icon in the top right corner (I think they call it the “Session Menu”, but it looks like a power button to me) and select “System Settings”. Under the “Internet and Network” heading, is an option called “Remote Desktop”. Click on that. Tick the top two boxes “Allow other users to view your desktop” and “Allow other users to control your desktop”. Tick the box “Require the user to enter this password” (and enter a password) and “Configure network automatically to accept connections”. Untick “You must confirm each access to this machine” and select “Only display an icon when there is someone connected”. Close it.

Now, try connecting to your device, and see what happens. I had some issues with Compiz elements not rendering correctly, and found a few hints to fix it. The first says to turn on the “disable_xdamage” option. It says to use gconf-editor, but I’m SSHing in, so I need to use gconftool-2 as follows:

gconftool-2 --set "/desktop/gnome/remote_access/disable_xdamage" --type boolean "true"

Personally, I only want to ever connect over OpenVPN to this, so I added the following:

gconftool-2 --set "/desktop/gnome/remote_access/network_interface" --type string "tun0"

You may wish to only ever access it over SSH, in which case replace “tun0” with “lo”

Now, I next made a big mistake. I followed some duff guidance, and ended up killing my vino server (I’m still not sure if I was supposed to do this or not), but to get it back, I followed this instruction to restart it. I had to tweak it a little:

sudo x11vnc -rfbport 5901 -auth guess

Once you’ve started this, tunnel an extra port (5901) to your machine, start VNC to the tunnelled port, and then go back through the options above. Exit your VNC session to the new tunnelled port, and then hit Control+C on the SSH session to close that x11vnc service.

Experimenting with Tiny Core Linux on QEMU

JonTheNiceGuy 3 Comments

In response to a post on the Ubuntu UK Loco mailing list today, I thought the perfect way to produce a cross-platform, stable web server… would be to create a QEMU bootable image of Tiny Core.

So, the first thing I did was to download a Tiny Core image. This I obtained from the Tiny Core Download Page. I then created a 512MB disk image to store my packages on.

qemu-img create tinycore-tce.img 512M

After a bit of experimenting, I ended up with this command to boot TinyCore. At the moment, it’s relatively cross-platform, but will need some tweaking to get to the point where I can do anything with it…

qemu -hda tinycore-tce.img -m 512 -cdrom tinycore-current.iso -boot d -net nic -net user,hostfwd=tcp:127.0.0.1:8008-:80 -vnc 127.0.0.1:0 -daemonize

So, let’s explain some of those options.

-hda tinycore-tce.img

This means, use the image we created before, and install it in /dev/hda on the visualised machine.

-cdrom tinycore-current.iso -boot d

Create a virtual CD using the ISO file we downloaded. Boot from the CD rather than any other media.

-m 512

Allocate the virtual machine 512Mb RAM.

-net nic -net user,hostfwd=tcp:127.0.0.1:8008-:80

Create a virtual network interface in “UserMode”, and port forward from port 80 on the dynamically allocated IP address on the virtual machine to port 127.0.0.1:8008 (which means it’s only accessible from the host machine, not from any other machine on the network)

-vnc 127.0.0.1:0 -daemonize

This makes the service “headless” – basically meaning it won’t show itself, or need a terminal window open to keep it running. If you want to interact with the system, you need to VNC to localhost. If you’ve already got a VNC service running on the machine (for example, if you’re using Vino under Ubuntu), increment the :0 to something else – I used :2, but you could use anything.

At the moment, because I’ve not had much opportunity to tweak TinyCore’s boot process, it won’t start running automatically (you have to tell it what to start when it boots), nor will it start any of the services I want from it, I’ve had to use VNC to connect to it. I’ll be trying out more things with this over the next few days, and I’ll update this as I go.

Also, I’ve not tried using the Windows qemu packages to make sure the same options all work with that system, and I’ll probably be looking into using the smb switch for the -net user option, so that as much of the data is clearly accessible without needing to drop in to the qemu session just to upload a few photos into the system. I guess we’ll see :)

A tip for users who SSH to a system running ecryptfs and byobu

JonTheNiceGuy Leave a comment

I’ve been an Ubuntu User for a while (on and off), and a few versions back, Ubuntu added two great installed-by-default options (both of which are turned off by default), called Byobu (a Pimp-My-GnuScreen app) and ECryptFS (an “Encrypt my home directory” extension).

Until just recently, if you wanted to enable both, and then SSH to the box using public/private keys, it would use the fact you’d connected and authenticated with keys to unlock the ECryptFS module and then start Byobu. A few months back, I noticed that if I rebooted, it wouldn’t automatically unlock the ECryptFS module, so I’d be stuck without either having started. A few login attempts later, and it was all sorted, but just recently, this has got worse, and now every SSH session leaves me at a box with an unmounted ECryptFS module and no Byobu.

So, how does one fix such a pain? With a .profile file of course :)

SSH in, and before you unlock your ECryptFS module run this:

sudo nano .profile

You need to run the above using sudo, as the directory you access before you start ECryptFS is owned by root, and you have no permissions to write to it.

In that editor, paste this text.

#! /bin/bash
`which ecryptfs-mount-private`
cd
`which byobu-launcher`

Then use Ctrl+X to exit the editor and save the file.

The next time you log in, it’ll ask you for your passphrase to unlock the ECryptFS module. Once that’s in, it’ll start Byobu. Job’s a good’n.

Watching for file changes on a shared linux web server

JonTheNiceGuy Leave a comment

$NEWPROJECT has a script which runs daily to produce a file which will be available for download, but aside from that one expected daily task, there shouldn’t be any unexpected changes to the content on the website.

As I’m hosting this on a shared webhost, I can’t install Tripwire or anything like that, and to be honest, for what I’m using it for, I probably don’t need it. So, instead, I wrote my own really simple file change monitor which runs as a CronJob.

Here’s the code:

#! /bin/bash
# This file is called scan.sh
function sha512sum_files() {
find $HOME/$DIR/* -type f -exec sha512sum '{}' \; >> $SCAN_ROOT/current_status
}
SCAN_ROOT=$HOME/scan
mv $SCAN_ROOT/current_status $SCAN_ROOT/old_status
for DIR in site_root media/[A-Za-z]*
do
sha512sum_files
done
diff -U 0 $SCAN_ROOT/old_status $SCAN_ROOT/current_status

And here’s my crontab:


MAILTO="my.email@add.ress"
# Minute Hour Day of Month Month Day of Week Command
# (0-59) (0-23) (1-31) (1-12 or Jan-Dec) (0-6 or Sun-Sat)
0,15,30,45 * * * * /home/siteuser/scan/scan.sh

And lastly, a sample of the output

--- /home/siteuser/scan/old_status 2010-10-25 14:30:03.000000000 -0700
+++ /home/siteuser/scan/current_status 2010-10-25 14:45:06.000000000 -0700
@@ -4 +4 @@
-baeb2692403619398b44a510e8ca0d49db717d1ff7e08bf1e210c260e04630606e9be2a3aa80f7db3d451e754e189d4578ec7b87db65e6729697c735713ee5ed /home/siteuser/site_root/LIBRARIES/library.php
+c4d739b3e0a778009e0d53315085d75cf8380ac431667c31b23e4b24d4db273dfc98ffad6842a1e5f59d6ea84c33ecc73bed1437e6105475fefd3f3a966de118 /home/siteuser/site_root/LIBRARIES/library.php
@@ -71 +71 @@
-88ddd746d70073183c291fa7da747d7318caa697ace37911db55afce707cd1634f213f340bb4870f1194c48292f846adaf006ad61b4ff1cb245972c26962b42d /home/siteuser/site_root/api.php
+d79e8a6e6c3db39e07c22e7b7485050007fd265ad7e9bdda728866f65638a8aa534f8cb51121a68e9287f384e8694a968b48d840d37bcd805c117ff871e7c618 /home/siteuser/site_root/api.php

While this isn’t the most technically sound way (I’m sure) of checking for file changes, at least it gives me some idea (to within 15 minutes or so) of what files have been changed, so gives me a time to start hunting.