Tag Archives: Ubuntu

CLI

Allow non-root users to mount disks

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I came across a need today to allow a regular (non-root) user to mount disks in Ubuntu 14.04 Trusty Tahr. I usually use sudo but in this case I needed to be able to run photorec as a regular user.

The way to accomplish this is to add the regular user to the disk group. To accomplish this, run this command:

sudo usermod -a -G disk <username>

If you are logged in as that user, you will have to log out and log back in to receive the permissions. Once this is done you should be able to mount disks without using sudo or being root.

Gaming, OS

Install ventrilo on Ubuntu 14.04 64bit

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Ventrilo is a voice communication server which is popular in the gaming community. It allows teams of people to get together and have voice chats. I recently tried to install vent on a 64bit instance of Ubuntu 14.04. When I tried to execute the server binary, I was greeted with this lovely error message:

bash: ./ventrilo_srv: No such file or directory

It’s a pretty cryptic error message that had me chasing my tail for a while until I came across this post which shed further light on the issue. This error stems from trying to run a 32bit binary on a 64bit system without the proper libraries installed.

A simple

sudo apt-get install lib32z1

Resolved this issue. After those 32bit libraries were installed, vent ran without issue.

CLI

Redshift – a better flux program for Linux

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F.lux is a wonderful tool for helping eye strain. People who stare at computer screens all day (like myself) can experience quite a bit of eye strain due to the harsh lights screens emit. One solution is to wear yellow tinted gamer goggles. I chose the cheaper route, installing software to adjust the color temperature of your monitor. Flux does this beautifully.. for Windows, at least.

Linux is a different story. Its GUI is pretty flaky and appears to only work for one screen. Enter Redshift, an updated fork of the Linux port of F.lux, which properly supports dual monitors. Unfortunately, it is harder to configure than F.lux. It is a command line only tool (with a GUI indicator component) and it requires creating a manual configuration file.

On my Linux Mint system (Ubuntu based) I needed to install the following:

sudo apt-get install redshift gtk-redshift

I had a hard time getting day/night changes to work. Redshift allows you to specify several different location options, but none of them appeared to work for me. I then realized that I like the softer colors of redshift all the time so I simply set the same temperature for day or night. It now doesn’t matter what the latitude / longitude is.

I found it odd that the settings for flux and redshift don’t appear to be the same. I tweaked my config a little bit to best closely match my Windows f.lux setup. Below is my config file, placed in ~/.config/redshift.conf.

; Global settings for redshift
[redshift]
; Set the day and night screen temperatures

temp-day=4500
temp-night=4500

; Enable/Disable a smooth transition between day and night
; 0 will cause a direct change from day to night screen temperature.
; 1 will gradually increase or decrease the screen temperature
transition=1

; Set the screen brightness. Default is 1.0
;brightness=0.9
; It is also possible to use different settings for day and night since version 1.8.
;brightness-day=0.7
;brightness-night=0.4
; Set the screen gamma (for all colors, or each color channel individually)
gamma=0.8
;gamma=0.8:0.7:0.8

; Set the location-provider: 'geoclue', 'gnome-clock', 'manual'
; type 'redshift -l list' to see possible values
; The location provider settings are in a different section.
location-provider=manual

; Set the adjustment-method: 'randr', 'vidmode'
; type 'redshift -m list' to see all possible values
; 'randr' is the preferred method, 'vidmode' is an older API
; but works in some cases when 'randr' does not.
; The adjustment method settings are in a different section.
adjustment-method=randr

; Configuration of the location-provider:
; type 'redshift -l PROVIDER:help' to see the settings
; ex: 'redshift -l manual:help'
[manual]
lat=40
lon=110

; Configuration of the adjustment-method
; type 'redshift -m METHOD:help' to see the settings
; ex: 'redshift -m randr:help'
; In this example, randr is configured to adjust screen 1.
; Note that the numbering starts from 0, so this is actually the second screen.
[randr]
screen=0

After saving the config file you can add gtx-flux  gtk-redshift as a startup application to have it automatically load on startup. My eyes feel much more comfortable now.

 

 

Virtualization

Convert xenserver .xva file to raw disk image

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What if you want to migrate a VM that’s been living on Citrix Xenserver to a different linux machine running vanilla Xen? The process isn’t as straightforward as you might think. Fortunately thanks to Eriklax over at github there is a fairly easy way to convert xenserver’s .xva virtual machines to other formats, via xva-img.

The first step is to download and install xva-img from github.

wget https://github.com/eriklax/xva-img/archive/master.zip
unzip master.zip
cd xva-img-master
cmake .
sudo make install

When trying to compile this on my Linux Mint Cinnamon machine I ran into the following errors:

CMake Error: your CXX compiler: "/usr/bin/c++" was not found.   Please set CMAKE_CXX_COMPILER to a valid compiler path or name.
xva-img-master/src/sha1.cpp:20:25: fatal error: openssl/sha.h: No such file or directory
 #include <openssl/sha.h>

I had to install the build-essential and libssl-dev packages in order to successfully compile and install xva-img.

Now that it’s installed, create a directory and extract your .xva file into it.

mkdir my-virtual-machine 
tar -xf <.xva file> -C my-virtual-machine 
chmod -R 755 my-virtual-machine

Once that’s finished (it might take a while – it took over an hour for me) the last step is to convert the extracted directories into a raw disk file.

Note:  when you extract your VM tar creates subfolders for each hard disk attached to the VM. You will have to run this command for each Ref folder that was generated as part of the image extraction process.

xva-img -p disk-export my-virtual-machine/Ref\:1/ disk.raw

It took a while for some reason, but it did eventually generate the desired image.

Now that I have a raw disk image I can transfer it to an LVM partition for use with xen:

sudo dd if=win8.1.img of=/dev/desktop-xen/Win8.1 bs=64M

Success.