Dragly » Ubuntu

Getting a headless connection to a server

Svenn-Arne Dragly — Wed, 25 Jan 2012 18:54:10 +0000

I just learnt how to get a headless connection to a server before it has even booted. This gives access to LUKS and LVM, giving the oppurtunity to decrypt an encrypted hard drive. The solution was in this blog post. I also found a post about this on Stack Exchange, which I decided to contribute to. For my own later reference, I’ll repost the walkthrough here.

—-

I have summarized what you need to do in the following. For more details, have a look at the post above:

Install BusyBox and Dropbear on your server
```
sudo apt-get install dropbear busybox 
```
Update your initramfs on the server
```
sudo update-initramfs -u 
```
Copy the private key generated by dropbear to your client machine. You may have to copy this to a new dir and change ownership to do this. On your serverdo the following:
```
sudo cp /etc/initramfs-tools/root/.ssh/id_rsa ~/. sudo chown user:user ~/id_rsa 
```
Remember to replace user with your username. Password logins don’t seem to work.
Now you may transfer the private key with scp by calling the following on your client:
```
scp user@remote.server:~/id_rsa ~/.ssh/id_rsa_dropbear 
```
Set up your client‘s ~/.ssh/config file for easy login. Open it up with a text editor and add the following:
```
Host myremoteserver
HostName my.remote.server
User root
UserKnownHostsFile ~/.ssh/known_hosts.initramfs
IdentityFile ~/.ssh/id_rsa_dropbear 
```
Change the Host to whatever you like and HostName to the name of your server. Let the user be root. It appears to be the only accepted user in Dropbear. Save and close the file.
Restart your server and wait for the passphrase prompt. Give Dropbear a few seconds to detect and set up its internet connection. Connect to your server with the following command on your client:
```
ssh myremoteserver # or any name you chose 
```
When logged in, issue the following command on your server. See the blog post for details:
```
pid=`ps | grep "/scripts/local-top/cryptroot" | cut -d " " -f 3`;
kill -9 $pid; sleep 35; /scripts/local-top/cryptroot;
pid=`ps | grep "/bin/sh" | cut -d " " -f 3`;
kill -9 $pid;
```
It will take some time (30 seconds) before you get to type your passphrase. Type it in when prompted.
Close the connection by typing
```
exit 
```
Your server should now have unlocked its encrypted hard drive and boot as normal.

(A huge thanks to the original author of the blog post!)

—-

Thunderbird with Lightning on Ubuntu

Svenn-Arne Dragly — Wed, 25 Jan 2012 12:42:19 +0000

I’m trying out Thunderbird with Lightning as my calendar application, but for some reason Lightning did not show up under Add-ons in Thunderbird. Instead I installed it by using the xul-ext-lightning package. However, this ended up with all options in Lightning grayed out. To fix this I had to install the libstdc++5 package as well, as reported in this forum thread.

This is strange, since it worked fine on a laptop i tried to install Lighting on just a few days ago. But in any case, it works now, so if you want Thunderbird with Lightning on Ubuntu and are having trouble installing it, you might want to try this command in a terminal:

sudo apt-get install thunderbird xul-ext-lightning libstdc++5

That should do the trick.

Bookmarks in terminal

Svenn-Arne Dragly — Tue, 01 Nov 2011 12:02:34 +0000

Today I found a great tool to ease the navigation in terminal, called apparix. It lets you bookmark a folder so that you easily can navigate to it just by typing

to nameofbookmark

To install apparix in Ubuntu, type

sudo apt-get install apparix

in a terminal window.

After installation you need to set up the aliases “bm” for bookmarking and “to” for going to a bookmark by adding a few functions to your .bashrc file in your home folder (if you don’t have this file, you can create it yourself).

You’ll find the functions you need to add by issuing the command

apparix --shell-examples

in a terminal window. Copy everything below “Bash-style functions” except the “CSH-style aliases”. Paste this into your .bashrc file.

Open up a new terminal, cd to your directory of choice and type

bm mybookmark

to bookmark the folder. Afterwards you can go to any folder and type

to mybookmark

to go to your bookmark.

This tool is of course available for other Linux distributions too.

Fixing the volume treshold and intervals in Ubuntu on Dell XPS M1330

Svenn-Arne Dragly — Thu, 13 Oct 2011 11:23:54 +0000

So the new Ubuntu version is finally out and as with every other time I’ve been upgrading from one version of Ubuntu to a new one, I keep forgetting how to fix the sound issue on the Dell XPS M1330. It is no big issue, really. It is simply that the lowest volume threshold is a bit high with headphones plugged in and that the volume intervals are a bit too large.

Fixing this is thankfully simple even though I keep forgetting. I guess this has to do with the fact that I’m only doing this once every six months.

If you’re having the same issue, open up a terminal and open the file “/etc/pulse/default.pa” in your favorite editor:

gksudo gedit /etc/pulse/default.pa

Change the line that says

load-module module-udev-detect

into

load-module module-udev-detect ignore_dB=1

Save and close the file.

Now, let’s restart pulseaudio and open alsamixer in terminal

pulseaudio -k
alsamixer

Use the arrow keys on your keyboard to bring down the PCM volume to about 50 % (or whatever suits your ears). Close alsamixer with ESC.

Now you should be able to enjoy your listening without blowing out your ears. Just note that whenever you are using your speakers and need them back at full volume, you might have to open up alsamixer again and bring the PCM volume back up.

Editing the default.pa file just makes pulseaudio respect your PCM setting. Otherwise it would set it to 100 % whenever you change the volume.

Spotify for Linux

Svenn-Arne Dragly — Mon, 27 Sep 2010 22:21:36 +0000

Awesome news! Spotify is now finally available as a native client for Linux. I have no idea why I haven’t spotted this earlier, as it was already announced in July, but in any case it is finally here.

Although they call it a preview, it seems to be a very finished and good-looking product, and I finally might get rid of those annoying sudden playback stops I experienced while Spotify under Wine. At least I haven’t experienced any of them yet.

I wish they would release it as an open source application as well, but for now, I’m very satisfied seeing that the money I’m spending on it pays off for Linux users as well. At the moment though, it seems like it is only packaged for Ubuntu and Debian, but hackers using other distros out there are probably going to figure out how to run it on other machines.

Now I’ll be hoping for a native version for N900, as most of the projects attempting to run Spotify on Maemo appear to be left unusable each time Spotify updates their API.

Connect to your N900 while developing via usb

Svenn-Arne Dragly — Sun, 18 Jul 2010 17:16:43 +0000

If you are developing for Nokia N900 using the Nokia Qt SDK, you are most likely following this guide to set up your environment. This is all nice and easy, but if you are connecting using usb you have to open a terminal each time you plug in your N900 and write

ifconfig usb0 192.168.2.14 up

If you, like me, get tired of doing this you may instead let Network Manager in Gnome do the work for you. First of all, connect your N900 via an available USB port. Next, right click the Network Manager icon and hit “Edit Connections…”.

This window will pop up. Press the “Add” button.

Type in a useful name, such as “N900 via usb”, and leave everything under “Wired” as is. Select the “IPv4 Settings” tab.

Set the Method to “Manual” and click “Add”.

Type in 192.168.2.14 as the address and 255.255.255.0 as the netmask. Leave the gateway blank.

Hit “Apply” and you are good to go!

Next, just click the Network Manager icon and select “N900 via usb”. If nothing went wrong, you should now be connected to your device, enabling you to use Qt Creator to its full extent. The next time you plug in your N900, Network Manager will do the work for you automatically.

Update: Note that if you already have a wired connection, Network Manager might try to connect to this so-called “Auto Ethernet” connection when you plug in. If this happens, just click the network manager icon and select the correct connection.

This might also happen the other way around, connecting to your USB connection with your Ethernet card, which of course won’t work. To avoid this completely, you might want to disable auto-connection for you N900 USB.

Why I’m not using Ubuntu One

Svenn-Arne Dragly — Mon, 15 Feb 2010 22:55:12 +0000

Recently I’ve had some issues with my previous solution for synchronizing files between my computers. I used to have an SSH server which I placed all my files on, and usually I edited them directly on this server. Whenever needed offline I used to synchronize them to my computers using Unison. Recently, however, the SSH connection to the server has been pretty sluggish on my laptop, causing the work flow to slow down.

I went looking for an alternative, and since Ubuntu comes with Ubuntu One preinstalled, I thought I should give it a try. The results were not even close to what I wanted.

First of all, there appears to be no kind of encryption on the Ubuntu One server – didn’t really bother me. I just set up an EncFS folder on my local computer and put all the files to synchronize inside this folder. The problem, however, occured when I needed to synchronize some of my papers while working on them. I went ahead and saved everything, waited a couple of minutes after seeing the message from Ubuntu One telling me that the files where syncing, and shut down the laptop. Back home, however, the sync would not start at first. I waited a little and when the sync seemed to have started, I opened the folder with the files – but, there where only my old files in there.

In frustration I picked up my laptop, put it on the desk, connected it to the Internet, and watched Ubuntu One sync the files over again. Wasn’t it supposed to do this four hours ago?

I went back to the main computer and looked at the folder, refreshed it, stared at it, cursed at it. Nothing happened. Not even after 30 minutes.

Okay. Back to looking for alternatives.

Spideroak and Dropbox

So, are all synchronization solutions this bad? You don’t have to worry, they are not even close!

I tried out Dropbox. Installed it and placed a few files in the Dropbox folder. Time to sync? I don’t have a clue. I didn’t even get to push the button on my stopwatch to check! Once the file was placed in the folder on my main computer, it was already on my laptop. Quite nice.

Spideroak on the other hand took 20 seconds or so before synchronizing, but that’s still an enormous improvement compared to Ubuntu One. And Spideroak has a couple of other benefits.

Where Dropbox only let’s you sync files in a specific folder, Spideroak let’s you set up several folders in different paths on your computer to sync. And you may also backup files which are not supposed to be synced.

The probably most important feature that Spideroak has is that the files are encrypted on each computer, making them unreadable even to the Spideroak employees. This is an important security measure which Dropbox lacks. On the other hand you could just put everything in an encrypted folder in the first place, which I think you should do even with Spideroak. The latter is because Spideroak decrypts the files when you watch them through the web-viewer, which means it’s technically possible to read your files when you are doing the same online.

Speed vs. features

I guess it’s up to you to decide what’s most important for you. The ease of use and speed which Dropbox offers, or the more advanced features and all over decent speed of Spideroak.

At the moment I’m running a sync of 900 MB of files using both solutions. I’ll update this post whenever they finish to give you some information about whether the speed differs on large synchronizations. Currently Dropbox is already syncing all the files, while Spideroak is “Pending new calculations”.

Fixing a bug with python-visual in Ubuntu Karmic

Svenn-Arne Dragly — Thu, 21 Jan 2010 12:42:00 +0000

I was preparing to do some tasks in my physics course today, and experienced a rather annoying problem when attempting to use the python-visual package in Ubuntu.

There seems to be a bug in Ubuntu Karmic which results in the following output when trying to run this command:

from visual import *

The output is as follows:

Traceback (most recent call last):
  File "cooper.py", line 1, in
    from visual import *
  File "/usr/lib/python2.6/dist-packages/visual/__init__.py", line 59, in
    import cvisual
AttributeError: 'Boost.Python.StaticProperty' object attribute '__doc__' is read-only

The fix is luckily quite simple.

Andrew Mitchell has a package repository for Ubuntu which contains an update to a library called “boost”. You can add this repository by selecting System > Administration > Software Sources. Then select “Other Software” and click on “Add…”.

Now, type in the following in the textbox:

ppa:ajmitch/ppa

Then click “Add source” and “Close”. If prompted, select “Reload” and then go to System > Administration > Update Manager. Click “Check” and then install all updates.

When this has been done, you are ready to run your python script.

Happy coding!

Mounting a Windows share folder in Ubuntu

Svenn-Arne Dragly — Tue, 09 Jun 2009 20:06:09 +0000

I have been connecting to my home folder at the Universitiy of Oslo for quite some time now, and since they use the Windows file-sharing protocol for this purpose, there has been room for quite som headaches.

After some googling I was able to figure out how to connect and mount a folder temporarily, but I had to re-mount it with my password every time I rebooted the computer. Finally, after realizing I actually tried this when I first figured the temporary method, I am now able to mount it permanently. I’ll show you how, in just a few, simple steps:

First of all, we need to install the samba file system. Type the following in to a terminal:

sudo apt-get install smbfs

Next, we need to get our username and password ready. Type the following into a terminal while replacing [your username] with your username:

gksudo gedit /home/[your username]/.smbcredentials

In the new file, add the following while using your own username and password:

username=[your username on the windows (smb) server]
password=[your password on the windows (smb) server]

Close the file, and type the following in to your terminal:

sudo mkdir /media/sambamount
sudo cp /etc/fstab /etc/fstab.backup
sudo gedit /etc/fstab

We have now made a backup of the current fstab (the file managing your mounted file systems) and opened it for editing. Add the following line to the file while substituting the brackets with your own values:

//[server name or DNS]/[folder on server to mount] /media/sambamount cifs credentials=/home/svenni/.smbcredentials,uid=[your local username],gid=users,iocharset=utf8 0 0

Save and close the file.

Everything should now be ready for the directory to be mounted when you boot the computer, but you could test it before you have to close the browser and take a two minute break away from your precious desktop.

Type the following into your terminal to test the mount:

sudo mount -a

Your shared windows directory should now appear on the desktop as a hard drive icon with the name «sambamount».