Welcome to The Linux Page

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This site is a collection of my own work with Linux. Certain things are easy, others take time to decipher and if I ever need to repeat the work (which usually happens!), then I need to remember everything by memory or... have a site with all the steps taken and to take again.

The following are my most recent posts:

Ever wondered how to verify the remote host fingerprint on SSH connect?

WARNING: This is actually wrong. The -F is a SEARCH feature. Not a way to recalculate the value on your own system. So you can verify that the value is the same in your database, but SSH already does that and shows you that terrible warning... so in effect it is the exact same command.

Whenever you connect to a computer with SSH, it gives you a fingerprint of the host.

Ever wondered how to check whether that fingerprint is a match? Yeah... I figured, 99% of us don't even know how to make sure that it is indeed a match.

There is the command line to generate that fingerprint:

...

Today I was testing a new intsallation that I prepared in the last month or so and once I hit Cassandra, I got this strange message:

   NoHostAvailable: ('Unable to complete the operation against any hosts',
   {<Host: 192.168.2.92 dc1>: Unavailable('Error from server: code=1000
   [Unavailable exception] message="Cannot achieve consistency level ONE"
   info={\'required_replicas\': 1, \'alive_replicas\': 0, \'consistency\': \'ONE\'}',)})

I looked for a solution with Google but was not really able to find anything that ...

Since I have several computers running Ubuntu, I like to have them up to date, but it always takes a bit of time to download the new packages. I think those should be downloaded only once and then shared between all my computers (I also run VPS which can benefit from this sharing.)

So, I decided to finally look into it and the simplest was to install apt-cacher-ng on my main server:

sudo apt-get apt-cacher-ng

That's it for the main server (from what I've read, at least, although I am thinking that maybe we need to tell apt-get to check that cache first even on the main system?)

...

I get a set of upgrades, about once a day these days (the Ubuntu and other Open Source developers are keeping way too busy!)

Because of that, I run the software updater. That takes time, generally. But why is that?

After various upgrades from one OS version to another, possibly from the start, I dunno exactly when it broke, but the autoremove feature stopped uninstalling the old kernels.

In itself, it is not so bad, you just get additional kernels under /boot. It can be come a problem if you have a small /boot partition, but otherwise, it is not a big problem in itself.

Until you upgrade!

Jira does not want to start?!

Jump start Jira

Today we were forced to transfer all our services from one server to another.

One of those services is Jira.

From what I have seen, there is no good documentation on our to migrate an instance of Jira from one Ubuntu server to another. Yet it is actually not that complicated.

Step 1. Make sure your current instance is not running

In order to avoid changes that would not make it to the new instance, make sure to stop Jira in the existing system. If you can, just stop Apache2 or whatever front end you are using.

Step 2. Copy the Data

Jira saves data in two locations: your database ...

Writing a Shell Script from cmake

In cmake, you have a cool feature which allows you to create a file.

First you use a WRITE, then you use the APPEND to add more lines to the file.

That file may be a shell script, though. In that case, you run in a problem whenever you want to write a variable which uses the curly brackets (as in ${TEST}), because cmake sees those as its own variables.

There is an example of script that we use in our Snap! development.

file( WRITE  ${lint_script} "#!${BASH}\n"                                                            )
file( APPEND ${lint_script} "if test \${3##*.} = ...

systemd — got to learn that one now

systemd has come as the default boot loader since Ubuntu 15.04. The old version, upstart, is now considered deprecated. Systemd has an interface pretty similar to the upstart service command line.

Command	Description	Support	Persist
systemctl start SERVICE	Start SERVICE	Always	No
systemctl stop SERVICE	Stop SERVICE	Always	No
systemctl restart SERVICE	Restart SERVICE	Always	...

I found the following in my logs, and thought it was very funny:

198.20.87.98 - - [22/Dec/2015:21:43:42 -0800] "GET / HTTP/1.1" 444 5666 "-" "-"
198.20.87.98 - - [22/Dec/2015:21:43:42 -0800] "GET /robots.txt HTTP/1.1" 444 5666 "-" "-"
198.20.87.98 - - [22/Dec/2015:21:43:42 -0800] "GET /sitemap.xml HTTP/1.1" 444 5666 "-" "-"
198.20.87.98 - - [22/Dec/2015:21:43:58 -0800] "quit" 405 5461 "-" "-"

The person who wrote this robot is not sending me who he is (last ...

The mouse pad worked just fine for days and "all of a sudden" my Acer, an Aquire R 14 (Acer Touch R3-471T), but it looks like many if not most Acers have the same issue.

The fact is that I use the Fn + F8 key to mute the speaker all the time, whenever there is an ad in a video, I really have to do that!

The Fn + F7, which is right next to the Fn + F8, is actually a key one can use to turn the Mouse Pad ON and OFF. Do it once again, Fn + F7, and the Mouse Pad will work again.

Hopefully you had a USB mouse or like me, you installed Synergy and thus could use your Linux mouse anyway. ...

I installed a website on a brand install installation of Ubuntu 14.04 (opposed to an upgrade from earlier versions) and the same website would not start...

Apache2 would give me the following error:

client denied by server configuration

which did not seem to tell me anything... I search for the error and the first page that popped up was a page by Apache2 and they said to add the deny/allow trick. I tried that and it did not help.

    <Directory /my/special/directory>
        Order allow,deny
        Allow from all
    </Directory>

Search further, I found an answer on ...

Unfreeze your Mouse when it Froze

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Step 1. Make sure your current instance is not running

Step 2. Copy the Data