The Tuxnetworks Linux Bible

Steam not starting from Cinnamon launcher

2022-09-29T07:27:00.001+10:00

Just upgraded to 22.04.1 LTS and of course that broke a lot of stuff.

In this case it was Steam (installed via apt repository)

Steam would start successfully from a terminal but would fail if launched from a launcher in Cinnamon. Further investigation showed that the steam process would be marked "defunct" after such a failure.

My initial workaround was to change the launcher to "Run in terminal" which worked OK but is kind of messy.

A better "fix" is to edit this file;

<code>sudo vi /usr/share/applications/steam.desktop</code>

and find this line;

<code>Exec=/usr/games/steam %U</code>

and change it to;

<code>Exec=bash -c "LD_PRELOAD='/usr/$LIB/libstdc++.so.6' DISPLAY=:0 steam</code>

Some ffmpeg usage examples

2019-06-17T06:24:00.000+10:00

Here are a few ffmpeg examples I have used on occasion:

Basic mkv to mp4 conversion
ffmpeg -i original.mkv -vcodec copy -acodec copy new.mp4

Advanced mkv to mp4 conversion (copy multiple streams)
ffmpeg -i original.mkv -map 0:a -map 0:v -map 0:s -c:v copy -c:a copy -c:a copy -c:s mov_text new.mp4

Transcode to huffyuv + flac
ffmpeg -i original.avi -f avi -c:v huffyuv -c:a flac new.avi

Copy video section (with audio)
ffmpeg -i original.avi -c:v copy -c:a copy -ss 00:00:03.000 -t 00:00:26.000 new.part.avi

Reverse video
ffmpeg -i original.avi -vf reverse -c:v huffyuv new.avi

Insert subtitles
ffmpeg -i original.mp4 -i subtitles.srt -c:v copy -c:a copy -c:s mov_text new.mp4

Concat multiple files
# cat part.list.txt
   file old.01.mp4
   file old.02.mp4
   file old.03.mp4

ffmpeg -safe 0 -f concat -i part.list.txt -c:v copy -c:a copy new.mp4

Convert DVD without transcoding
ffmpeg -i concat:VTS_07_1.VOB\|VTS_07_2.VOB\|VTS_07_3.VOB -map 0:v -map 0:a -c:v copy -c:a copy new.avi

Slow down video
ffmpeg -i input.avi -filter:v "setpts=2.0*PTS" -c:v huffyuv output.avi

Speed up video
ffmpeg -i input.avi -filter:v "setpts=0.5*PTS" -c:v huffyuv output.avi

Create and install an SSL certificate in Apache

2019-05-06T10:47:00.002+10:00

Lets create a SSL encrypted website using apache.

Prequisites:
A working unsecured website on port 80

If your server is behind a firewall you will need to open/forward port 443

A publicly accessible FQDN is configured for the site.

Enable ssl on apache;

sudo a2ensite default-ssl.conf

Installing certbot;

sudo apt install certbot python-certbot-apache

Use certbot to create a free certificate;

sudo certbot --apache certonly

Follow the prompts, they are self explanatory.

Note: This will break if the certbot cannot resolve your domain name properly. I have used the --certonly flag to stop certbot from editing apache configs because I prefer to do it myself. Apparently if you drop that flag you can skip the next step.

Once you are done you should have a shiny new certificate in /etc/letsencrypt/live/www.example.com/

Now, if you did not allow certbot to modify your apache configs you will need tell apache to use your new certificate.

Edit the file that contains the virtualhost configuration for your web site. The virtualhost section should look like this;

ServerName www.example.com
ServerAdmin brettg@tuxnetworks.com
DocumentRoot /var/www/html

(...)

Modify it to look like this;

ServerName www.example.com
ServerAdmin admin@example.com
DocumentRoot /var/www/html
SSLEngine on
SSLCertificateFile /etc/letsencrypt/live/www.example.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/www.example.com/privkey.pem

(...)

Restart your apache server and you should now be able to browse your site using https.

Note: If you want your site to work in both encrypted (SSL) mode as well as unsecured mode then when you are modifying the virtualhost config in apache copy that entire section to the end of the file and make the changes shown above in the new section

Cleaning up df output

2019-03-19T10:11:00.000+11:00

I use df a lot on ubuntu. Unfortunately with advent of snap devices df output has become increasingly cluttered with various devices mounted by the system that I generally don' have an interest in seeing.

For example:

# /bin/df
Filesystem 1K-blocks Used Available Use% Mounted on
udev 8121812 0 8121812 0% /dev
tmpfs 1630708 1888 1628820 1% /run
/dev/sda1 30627388 15252072 13796484 53% /
tmpfs 8153528 68012 8085516 1% /dev/shm
tmpfs 5120 4 5116 1% /run/lock
tmpfs 8153528 0 8153528 0% /sys/fs/cgroup
/dev/loop1 93184 93184 0 100% /snap/core/6405
/dev/loop2 93184 93184 0 100% /snap/core/6350
/dev/loop4 35456 35456 0 100% /snap/gtk-common-themes/818
/dev/loop7 35712 35712 0 100% /snap/gtk-common-themes/1122
/dev/sda2 76766240 26915652 45927952 37% /home
/dev/sdb 7814026584 7137072996 674941212 92% /mnt/library
/dev/sdc 3907018584 3436394816 467552000 89% /mnt/archive
tmpfs 1630704 16 1630688 1% /run/user/132
tmpfs 1630704 80 1630624 1% /run/user/1000
/dev/loop8 36224 36224 0 100% /snap/gtk-common-themes/1198
/dev/loop9 93312 93312 0 100% /snap/core/6531
/dev/loop0 48768594 48768594 0 100% /mnt/loop/Archive.TV.01
/dev/loop3 48628258 48628258 0 100% /mnt/loop/Archive.TV.02
/dev/loop5 48845728 48845728 0 100% /mnt/loop/Archive.TV.03

So that you don't have to visually hunt through that junk to see what you need add this to your users .bashrc file:

function df
{
/bin/df "$@" | grep -v loop | grep -v tmpfs | grep -v udev
}

Now your df output just lists the actual mounted drives:

#df

Filesystem 1K-blocks Used Available Use% Mounted on

/dev/sda1 30627388 15252080 13796476 53% /

/dev/sda2 76766240 26915652 45927952 37% /home

/dev/sdb 7814026584 7137072996 674941212 92% /mnt/library

/dev/sdc 3907018584 3436700752 467246064 89% /mnt/archive

/dev/loop0 48768594 48768594 0 100% /mnt/loop/Archive.TV.01

/dev/loop3 48628258 48628258 0 100% /mnt/loop/Archive.TV.02

/dev/loop5 48845728 48845728 0 100% /mnt/loop/Archive.TV.03

If you want see the full output use the full path /bin/df

autofs: keep devices permanently mounted

2019-03-19T09:59:00.000+11:00

I have some ISO images which I use autofs to mount as loop devices.

For reasons that are not important I want them to stay mounted permanently.

I couldn't find any information online on how to do this so I poked around in the related autofs man pages.

I noticed that there is a time out option which is set by default to 600 seconds.

I wondered what would happen if I set that to 0 seconds so I tried it.

So far the devices in question have stayed mounted for 15 minutes

Here's how to do it:

/etc/auto.master
/mnt/loop /etc/auto.loops -t 0

/etc/auto.loops

* -fstype=iso9660,loop :/store/ISO.archives/&.iso

The -t 0 is where we set the time out to 0 (infinite)

In case you are wondering the * at the beginning and the &.iso at the end of auto.loops will mount all of the iso files found in the /store/ISO.archives/ directory.

Virtualbox USB devices (updated)

2018-11-02T11:38:00.001+11:00

I have updated an old article about using USB devices in Virtualbox;

USB Devices in VirtualBox guests

Steam controller doesn't work in Ubuntu 18.04

2018-09-03T11:59:00.000+10:00

After upgrading or fresh install of Ubuntu 18.04 your previously working Steam controller will no longer be detected.

To fix this you must install a new package;

sudo apt install steam-devices

Extract subtitles as SRT from mkv

2017-12-22T09:36:00.001+11:00

mkvextract tracks source.mkv track_number:file.srt

You can obtain the track number using mkvtoolnix-gui or mkvinfo

Querying video file metadata with mediainfo

2017-10-06T09:29:00.001+11:00

I am working on a script that will query media files (mp4/mkv videos) to obtain metadata that can be subsequently used to rename the file to enforce a naming convention. I use the excellent mediainfo tool (available in the standard repositories) to do this.

mediainfo has a metric tonne of options and functions that you can use for various purposes. In my case I want to know the aspect ratio, vertical height and video codec for the file. This can be done in a single command;

mediainfo --Inform="Video;%DisplayAspectRatio%,%Height%,%Format%"

This works fine and returns something like this;

1.85,720p,AVC

When I say it works fine I mean it works fine in 99% of cases. The other 1% are made up of files that contain more than one video stream. Sometimes people package a JPEG image inside the container which is designated internally as "Video#2". In such cases the above command will also return values relating to the JPEG image producing something like this;

1.85,720p,AVC1.85,720p,JPEG

When this happens my script breaks. The workaround for that is to pipe the results through some unix tools to massage the output;

mediainfo --Inform="Video;%DisplayAspectRatio%,%Height%,%Format%\n" "${_TARGET}" | xargs | awk '{print $1;}'

Things to note in the revised command. There is a carriage return ("\n") at the end of the --Inform parameters which will put the unwanted data on a new line like this;

1.85,720p,AVC
1.85,720p,JPEG

xargs will remove that line feed and replace it with a space;

1.85,720p,AVC 1.85,720p,JPEG

And finally awk will produce only the first "word" (space delimited) from the result, which produces the desired output.

1.85,720p,AVC

Now obviously this method assumes that the first video stream in the container is the one we are interested in. I'm struggling to imagine a scenario where this would not be the case so at this point I am OK with that. If I find a file that doesn't work I might have to revise my script, but for now I will stick with this solution.

Virtualbox remote desktop

2017-08-26T15:07:00.000+10:00

I just had a frustrating couple of hours trying to get remote desktop working for a Virtualbox guest.

First, even though the settings screen implies that you merely need to turn remote support on you must also have the virtualbox extension pack installed.

Secondly, if you get "connection refused" or similar errors from the rdesktop client then you are probably using virtualbox 5.0.40

It wasn't until I upgraded virtualbox to 5.1.16 that it just magically started working. grrr

Booting Windows as either dual-boot physical machine or as a Virtual machine

2017-07-21T11:10:00.000+10:00

How to boot Windows as either dual-boot physical machine or as a Virtual machine

Here is a scenario.

You have a Linux PC that you want to also dual boot to Windows. That's not hard to do right?

Unfortunately though, we all know dual booting is a bit of a pain when you just want to do something quick in Windows. You need to close everything you are doing in Linux just to boot into Windows.

One solution to that is to run Windows in a VM, that's been possible for years now right? Well the problem with that is that sometimes you need to run native Windows to say, play a 3D game.

You could maintain 2 Windows systems, one via dual-booting and the other as a VM but who wants to maintain two copies of Windows?

This is what I do.

Our starting point is a Linux system on one disk (/dev/sda). We will be installing Windows on to a separate disk that is currently empty (/dev/sdb)

WARNING: If you muck this up you can destroy all the data on your Linux system. Make sure you have backups of everything and you are abso-fricking-lutely sure you have identified the correct drive devices

You can check your disks using this command:

sudo fdisk -l

For the remainder of this tutorial I will be using /dev/sdb for the drive that will host Windows 7.

Let's get started!

In your Linux installation you want to add your user to the "disk" group:

sudo usermod -a -G disk brettg

This allows your user to access the physical drive that Windows 7 is installed on.

Note: You will need to logoff and log back in again for this change to take effect.

Install Virtualbox:

sudo apt install virtualbox

Create a place for your Virtualbox disk images:

mkdir -p $HOME/VirtualboxImages/

Create a new virtual disk that references the physical drive that Windows 7 will be installed on:

VBoxManage internalcommands createrawvmdk -filename $HOME/VirtualboxImages/Windows7.vmdk" -rawdisk /dev/sdb

Open up Virtualbox and create a new virtual machine selecting "Use an existing virtual harddisk file" when you are setting it up.

Insert your Windows CD into the virtual machine (either as a physical CD or an ISO image).

Start the VM and go through the normal Windows installation process, then log into Windows.

Open the registry editor. Edit the following keys and set them all to 0:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\atapi\Start

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\intelide\Start

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\pciide\Start

This forces Windows to install and load three types of disk drivers at boot. (I don't know why you need to set these to zero). By default it just installs the driver that was needed at install time. This is requireed because when we try and boot Windows later it will not be able to read the disk because it doesn't have the proper driver for it.

Shutdown the VM

You will need to add your Windows disk to grub:

sudo update-grub

Now, hopefully if everything went according to plan you should be able to reboot and find Windows listed in your grub menu. Select that and boot into Windows.

Once you are in Windows, you will have to do all the usual driver installs etc but you already knew that right?

Have fun!

Note: Tested with Ubuntu 16.04.1 host and Windows 7/10 guests

Using H.265 (HEVC) on Ubuntu

2017-01-24T10:09:00.000+11:00

If you google search how to install H.265 on ubuntu you get a a bunch of posts that describe how to add a PPA for the necessary files.

However the repository hasn't been updated since 2015 (vivid vervet)

If you try to use the vivid repo then things fail because of dependency issues.

But not to worry as it seems that H.265 is now included in the standard xenial repository.

apt-cache search x265
libx265-79 - H.265/HEVC video stream encoder (shared library)
libx265-dev - H.265/HEVC video stream encoder (development files)
libx265-doc - H.265/HEVC video stream encoder (documentation)
x265 - H.265/HEVC video stream encoder

So, all you need to do is;

sudo apt-get install x265

and you are good to go.

Descreen images in Gimp

2015-12-31T09:39:00.000+11:00

I needed to remove the moire patterns of a scan. After a quick search on google I found this descreen plugin.

Unfortunately this plugin also requires the FFT gimp plugin, which is old and requires compiling and that page describes installing it for Windows.

This in turn was a bit of a problem because the FFT plugin has a few dependencies that aren't adequately documented.

To successfully build the plugin you need to first install libgimp-dev and libfftw3-lib packages from the standard repositories (debian/ubuntu)

# sudo apt-get install libfftw3-dev libgimp2.0-dev

Follow this by extracting the tar archive somewhere and doing

# make && make install

Once this is done, grab the descreen.scm file from the first link and plop it into ~/.gimp2.8/scripts

After starting gimp up there should be a "descreen" option under Filters->Enhance

Wordpress Warning

2015-06-29T11:02:00.001+10:00

Just a warning about Wordpress. If you create a Wordpress account you cannot delete it.

Their "delete your account" webpage only tells you how to remove a blog. The best advice they can give you is to make your account inactive. You can't delete it.

Find open files on a filesystem in FreeBSD

2015-06-29T09:27:00.002+10:00

I had a problem on an archaic FreeBSD machine whose /var filesystem had tipped over the 80% threshold of our monitoring system.

A brief investigation showed that there was a vast discrepancy between the output of the du and df commands.

The df command showed that the file system was 81% full where the du command showed it was around 5% full.

This situation is caused when a file is deleted but a process keeps it open. The difference is due to the different ways that the df and du commands calculate free space vs used space. This means that the disk space will still be reserved and therefore seen by df, but since du will no longer see a reference to that file in the directory tree, it cannot see those reserved blocks resulting in a difference between reported disk usage.

So, the next step is to find what process is holding a deleted open. Unfortunately, I would normally use something like lsof to do this but on this ancient version of freebsd that is not an option, so a new option is required.

# fstat -f /var

USER CMD PID FD MOUNT INUM MODE SZ|DV R/W

root fstat 13839 wd /var 94208 drwxr-xr-x 512 r

root csh 13582 wd /var 94208 drwxr-xr-x 512 r

operator csh 6713 wd /var 188489 dr-xr-xr-x 512 r

nobody snmpd 83626 3 /var 259076 -rw-r--r-- 2766247084 w

root cron 1287 wd /var 376832 drwxr-x--- 512 r

root cron 1287 3 /var 164874 -rw------- 4 w

_bgpd bgpd 1251 root /var 47104 dr-xr-xr-x 512 r

_bgpd bgpd 1251 wd /var 47104 dr-xr-xr-x 512 r

_bgpd bgpd 1251 jail /var 47104 dr-xr-xr-x 512 r

_bgpd bgpd 1250 root /var 47104 dr-xr-xr-x 512 r

_bgpd bgpd 1250 wd /var 47104 dr-xr-xr-x 512 r

_bgpd bgpd 1250 jail /var 47104 dr-xr-xr-x 512 r

dhcpd dhcpd 1213 6 /var 400402 -rw-r--r-- 45998 w

root syslogd 930 3 /var 164883 -rw------- 3 w

root syslogd 930 12 /var 259338 -rw-r--r-- 12844 w

root syslogd 930 13 /var 259324 -rw------- 78 w

root syslogd 930 14 /var 259278 -rw------- 40072 w

root syslogd 930 15 /var 259083 -rw------- 62 w

root syslogd 930 16 /var 259301 -rw------- 83687 w

root syslogd 930 17 /var 259077 -rw-r----- 1953 w

root syslogd 930 18 /var 259079 -rw-r--r-- 62 w

root syslogd 930 19 /var 259085 -rw------- 62 w

root syslogd 930 20 /var 259087 -rw------- 103292 w

root syslogd 930 21 /var 259284 -rw------- 78 w

root syslogd 930 22 /var 259084 -rw-r----- 62 w

root syslogd 930 23 /var 259082 -rw-r----- 62 w

We can see from the output of the fstat command that the snmp daemon has a 2.7Gb file open.

I killed and restarted snmpd and file system usage dropped down to 3%

Note: You could limit that output to only show files that are deleted (unowned) by grepping for "nobody"

# fstat -f /var

nobody snmpd 83626 3 /var 259076 -rw-r--r-- 2766247084 w

Configuration management: Salt vs Puppet

2015-04-09T11:51:00.000+10:00

I've spent some time experimenting with puppet and I have come to the conclusion that I don't much like it.

There are several reasons why this is the case but the main ones are the module system that it uses and the way it abstracts away the configuration details on the client.

Note: I gave up on puppet after only a couple of days after reaching a point where there was an error somewhere which was impossible to understand because it had no logical behaviour. Therefore I don't profess to be an expert on puppet to any degree at all so any comments from here on are merely my opinion and will definitely include liberal amounts of my misunderstanding of how Puppet works. That is another one of the problems I had with Puppet. The errors it produces are cryptic and there are so many things going on in the box of smoke and mirrors that you can't see the workings of that it is extremely hard to comprehend and debug things. Especially as a n00b.

From what I have managed to partially understand, Puppet ships with a bunch of pre-installed modules for common applications (such as apache) so you don't need to find and download the appropriate module.

This is all good of course until you need to do something that is not included by default. In that case you need to get on the Internet and find the module you need and install it. Sometimes there will be an "official" puppetlabs module and sometimes you need to trawl through many community provided modules of varying degrees of quality to find one that looks like it might do what you want. This in itself is not terrible but it does involve a lot more mucking about than I think should be required.

Once you have all your modules in order you need to start configuring stuff and this is where the frustration really kicks in.

Puppet uses a bunch of "manifest" files that must be created for each service, host, or groups of hosts. Manifests can include other manifests and everything must be carefully declared in the right places or else things just don't work, and most of the time you will get an obtuse error message that doesn't help a great deal in tracking things down.

Circular dependencies can be common without due care being taken.

For example, the straw that broke the proverbial camels back for me and turned me away from Puppet was where I had two similar hosts with two identical manifests that despite that would produce different results when trying to update them.

One would fail with "Error: Failed to apply catalog: Could not find dependency File[/etc/postfix/main.cf]" while the other one worked fine. This was strange to me because

a) the file it was complaining about existed on both hosts and

b) nowhere was I even trying to manage postfix.

I even went to the length of creating two completely empty manifests for the two hosts that still produced the same dissimilar results.

Somewhere in the "box of smoke and mirrors" something was going on but I could not for the life of me figure it out. I even posted a question on serverfault (I rarely need to go to that extreme) but the kind folks there were unable to help either.

So I just gave up because life is too short for that crap.

There are other reasons that I dislike puppet.

A major one is how it abstracts out configuration details for the hosts it manages.

To explain what I mean I will return to the example of apache from before. Now, I am fairly familiar with apache, and I know my way around the apache config files reasonably well. Consider this snippet:

ServerName webserver01.tuxnetworks.com

<VirtualHost first.example.com:80>
ServerAdmin brett@mydomain.com
DocumentRoot /var/www/first
</VirtualHost>

That is a pretty simple config for a global server name and a virtual host in apache.

Now, let's look at how you configure that in puppet.





class { 'apache':

 default_mods   => true,

}



apache:servername { 'webserver01.tuxnetworks.com' }



apache::vhost { 'first.example.com':

  port    => '80',

  docroot => '/var/www/first',

}

Now this is just a really simple example, but you will note the syntax that you are required to learn and use is totally different to how the target application would normally be configured. Things get even more excitingly confusing when you are trying to configure a service that you are not familiar with. In such cases you are not only required to first figure out what the native settings you need to put in the config file should be but then you must also figure out the correct Puppet syntax for getting there.

I had to do that just yesterday to add another domain to a haproxy server.

You will also note that the ServerAdmin variable has not been set in the puppet example because the 5 minutes that I spent searching the Internet on how to do it came up with nothing. I'm sure with more time I could find the answer (and there is a good chance just adding "serveradmin => brett@mydomain.com'" in there would work) but the point is that I really don't want to have to deal with this level of abstraction for something that I already know how to do.

So, given that you already think that the concept of configuration management systems is great but you are not prepared to devote the rest of your life wrestling with puppet then what do you do?

Well, another popular system is Chef, but after doing some research I concluded that Chef had almost as many idiocyncracies as Puppet so I have decided to explore the possibilities of saltstack.

So far I've managed to do most of what I want to do with salt and it has been far easier to get my head around it than I found with puppet, although there are still some conceptual things to understand as well as some gotchas that can stall things early on.

Come back later for a post on getting things up and running if you are interested.

The first good thing is that Salt does not require modules.

Another good thing is that Salt does not abstract away configuration details for most use cases.

Note: Salt has something called "pillars" that I have no understanding of. From what I have read these can get a bit more complex but for my purposes (installing packages & pushing configuration files) I have not yet needed to use those. If my requirements get more complex then I may have to visit them but the point is that as a new salt user you don't need to use them)

Anyway, on a salt server, you would simply copy a working apache.conf over to a directory on the salt-master and the minions will just use it as is. Simples!

But what if you need to set some of those details on a per host basis I hear you ask? For example maybe I want to set the ServerName directive to be whatever the hostname of the server is?

In that case all I need to do is modify it like so:

ServerName {{servername}}

<VirtualHost first.example.com:80>
ServerAdmin brett@mydomain.com
DocumentRoot /var/www/first
</VirtualHost>

What I have done there is simply replaced the server name string to become a variable place holder that can be used by the jinja templating engine that salt uses to insert the proper data whenever the minion is updated.

I don't need to learn a whole new syntax because I can just use the standard Apache conf layout that I am already familiar with and make certain parts of it "variable" as required.

Salt really is in my humble opinion much simpler to get up and running (but that may just be because I'm a bit thick of course). Also no offence intended to the folks who love Puppet, I know it is widely used out there and I still have an inherited puppet system here at work. The bottom line is that OSS is all about choice after all.

That is not to say it is perfect however. The documentation leaves a lot to be desired for instance, which is a pretty big problem in itself.

Anyway, stay tuned for a quick start guide to SaltStack at a later date.

FIX: master and slave have equal MySQL server UUIDs

2014-12-12T11:22:00.002+11:00

Newer versions of mysql use a unique UUID to do what the server variable server-id used to do.

That means if you need to do master/slave db replication each server will need its own UUID.

If the two servers have the same UUID, you will receive an error when attempting to sync the slave to the master:

master and slave have equal MySQL server UUIDs

If you are creating servers those servers from a virtual machine template then you will need to clear the UUID on each copy you make.

To do this, stop the mysql server and simply remove the file that contains the UUID

rm /var/lib/mysql/auto.cnf

When you start the server again it will generate a new one automatically.

nvidia optimus

2014-10-07T16:44:00.004+11:00

Trying to setup Mint Debian on a laptop with nvidia "optimus" is a bit different than the normal routine.

If you just install the nvidia-driver package and do nvidia-xconfig then when you try and reboot X will fail to start with;

"(EE) No Screens Found(EE)"

The reason for this is that the dual video card arrangement that Optimus provides is not supported "out of the box". You need to do a bit of extra work to get it working.

I am assuming that you have already installed the nvidia-drivers and linux kernel headers at this stage.

Next thing to do is make sure you remove /etc/X11/xorg.conf if you already have created that by using nvidia-xconfig. In fact at this point I recommend you remove nvidia-xconfig from your system entirely.

Next install some packages;

apt-get install bumblebee bumblebee-nvidia primus

Now, it would be nice to think that would be it but we do need to edit a file to get things working;

vi /etc/bumblebee/bumblebee.conf

Towards the bottom of the file in the [driver-nvidia] section change this line to look like this;

KernelDriver=nvidia-current

Reboot and you should be good to go.

You can test this by running this command;

optirun glxgears

Windows 7 refuses to reconnect to Samba after reboot

2014-10-02T16:38:00.001+10:00

Faaaaaark! I have been fighting this off and on now for weeks.

The scenario is this:

The network is a Windows domain. Let's call the domain "WINDOZESUX"

I have a Linux host running Samba that is not a domain member. Let's call it "sambaserver"

sambaserver is configured with:

workgroup = WINDOZESUX

Result: Windows 7 client can successfully mount \\sambaserver\share

That's cool.

Move forward until one of the Windows 7 clients reboots.

Result: Windows 7 client cannot reconnect to the samba share "The user name is not found"

Solution: Delete the saved credentials on the Windows client

Result: Windows 7 client can successfully mount \\sambaserver\share

Rinse, lather repeat.

Much troubleshooting follows. Eventually I had a dim recollection that I had "fixed" this once before by using an IP address instead of DNS

Solution: Use an IP address in the UNC path

Result: Windows 7 client can successfully mount \\1.2.3.4\share

Reboot and the share connects automatically without trouble. yay

Now, I was going to leave it at that (and I have for a while) but I really don't want to hard configure IP addresses all over the place because it can become a management disaster for the future.

Now, I have spent hours googling, found thousands of posts for basic errors such as noobs who just didn't have their DNS configured properly at, also a bunch of other posts suggesting that the share was trying to reconnect before the network adapter had come up which plainly was not the case because it worked fine with an IP address. No it was something do with DNS or WINS resolution. Or so I thought.

Suffice to say I spent a lot of time mucking about with WINS, DNS and SAMBA configurations and nothing made a lick of difference.

Eventually while clutching at straws I changed the sambaserver configuration to:

workgroup = LINUXROX

Went through the rinse, lather and repeat process and still it behaved in the same infuriating fashion.

Then while I was poking around in the Windows credential manager, about to delete the credential for the hundredth time, I clicked on "Edit credential"

Lo and behold, the username in the credential manager was shown as WINDOZESUX\username where I am sure the last time I had connected to the share it was using LINUXROX\username

Hmmm. So I changed the entry in the credential manager to the correct LINUXROX\username and rebooted again.

Result: Windows 7 client successfully remounts \\sambaserver\share

FFS. So it appears Windows has a bug (which knowing Microsoft may in fact be a feature) where when you connect to a non domain share from a domain member it does it correctly but when it saves the credentials it goes and changes the goddamned domain from the one you had specified to the domain that the client is on. But it only does that when you use a DNS name. When you use an IP address it works fine. Who knows why? Will Microsoft fix it? Why would they. They might however put up a technet article one day suggesting the solution is to buy a windows server you smelly Linux user.

God I hate Microsoft crap.

In other news, Bordlerlands 2 was just released on SteamOS/Linux!

Recovering a deleted file that is still held open

2014-08-28T13:45:00.000+10:00

I accidentally deleted the disk image file for a running virtual machine. oopsy!

Luckily, there is an easy way to undo that using the lsof command!

lsof | grep /home/qemu/images/my-disk-image.qcow2

This produces output like this;

qemu-kvm  24816      root    9u      REG              253,2 214781394944   21102665 /home/qemu/images/my-disk-image.qcow2 (deleted)

Take note of the first two numbers, which in my case are 24816 and 9 (Note: you must strip the trailing char from the second number)

Pause the VM (don't stop it!) so that the disk is not being written to while we do the next step.

Now you just need to copy the deleted file back to somewhere safe;

[root@devkvm03 images]# cp /proc/24816/fd/9 my-disk-image.qcow2

Using docker on Linux Mint Debian Edition

2014-07-22T15:12:00.003+10:00

Installing Docker on LMDE takes a few steps and will require that we add a third-party repository.

Note: We will be logged in as root to issue these commands. Also, I am by no means an expert on this, I am learning this as I go on.

So, with that out of the way let's add the key for the get.docker.io repository;

# apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 36A1D7869245C8950F966E92D8576A8BA88D21E9

Next add the repository to your apt sources;

# echo "deb http://get.docker.io/ubuntu docker main" > /etc/apt/sources.list.d/docker.list

Update apt;

# apt-get update

Install docker;

# apt-get install lxc-docker

Verify that it has worked by downloading and running the ubuntu container;

# docker run -i -t ubuntu /bin/bash
Unable to find image 'ubuntu' locally
Pulling repository ubuntu
e54ca5efa2e9: Download complete
511136ea3c5a: Download complete
d7ac5e4f1812: Download complete
2f4b4d6a4a06: Download complete
83ff768040a0: Download complete
6c37f792ddac: Download complete
root@46ec4b13f756:/#

Congratulations you are sitting in bash inside your ubuntu container. Type 'exit' or use ctrl-d to exit.

Note: It is important to understand that once you exit a container it ceases to run unless you specifically tell it not to (see below). It is not like a normal virtual machine that keeps on running in the background until you shut it down. To exit a container and have it remain running, use ctrl-p followed by crtl-q.

You probably dont want to be the root user every time you use docker. In that case simply add your user to the docker group;

# usermod -a -G docker myusername

You can list all the running containers with the 'docker ps' command. Add '-a to see the stopped ones as well.

Note: The containers that you create are kept in '/var/lib/docker/containers'

That's the basics of docker. The next thing to learn more about is using docker files to build containers.

Using SSMTP to send mail via gmail UPDATED

2014-07-11T12:10:00.000+10:00

I have updated the post that explains how to use SSMTP to send emails

Libvirt/qemu/kvm as non-root user

2014-07-02T14:52:00.000+10:00

Prerequisites:

A server with KVM

I'm going to use the qemu user that is created when you install KVM but you could use any user you like.

First, your user should belong to the kvm group:


grep kvm /etc/group
kvm:x:36:qemu

Create a libvirtd group and add your user to it



groupadd libvirt

usermod -a -G libvirt qemu

Create a new policykit config to allow access to libvirtd using your user account via ssh



vi /etc/polkit-1/localauthority/50-local.d/50-libvirt-remote-access.pkla

Add the following content:



[Remote libvirt SSH access]

Identity=unix-group:libvirt

Identity=unix-user:qemu

Action=org.libvirt.unix.manage

ResultAny=yes

ResultInactive=yes

ResultActive=yes

Restart libvirt

service libvirtd restart

Configuring a Printer With CUPS Web Admin

2014-07-01T14:44:00.003+10:00

I couldn't get the printer admin applet in Mint to add a new printer. It just kept saying "Failed to add printer" every time.

Then I discovered that CUPS has a web admin page:

http://localhost:631

When it ask for a username & password just enter any user with sudo privileges and you are in.

FIX: Black screen at login for LMDE/Cinnamon

2014-06-29T10:53:00.000+10:00

So, I installed a fresh copy of LMDE on a machine. Obviously, that will include doing an apt-get dist-upgrade to ensure every thing is all up to date.

After doing that, I restarted the box and got the Mint login screen, entered my password and got . . . . . a black screen with a mouse pointer and nothing else.

I couldn't find an answer on the Internet so eventually I took a punt and entered:

apt-get install cinnamon

and what would you know, Cinnamon wasn't installed at all. For some, the distribution upgrade had decided to remove Cinnamon altogether. After the install finished I rebooted and all was good again.