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Attacks by ZmEu or w00tw00t robots

Who is ZmEu?

An image showing ZmeuThe name Zmeu (no capital E) is the name of a fantastic creature of Romania. There are so many stories that there isn't a clear understanding of what it is... but it is human like, can spit fire and wants to marry young women.

If you're wondering, it is generally a bad guy.

ZmEu Attack

Today, I noticed a lot of traffic on one of my servers. Looking into what was happening, I immediately found out that an attacker was looking for a loophole in that system. That attack was being performed from China.

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

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:

    ssh-keygen -l -F <HOSTNAME>

This will print exactly the same value, assuming hostname represents the same computer (i.e. same IP address.) To compare, you may use something like this:

   if test "<ssh presented key>" = "<keygen presented key"; then echo ...

Unable to complete the operation against any hosts — from Cassandra

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 ...

Add a cache to upgrade your LAN servers faster

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?)

...

Why are my Ubuntu/Debian computer upgrades so slow?

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?!

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 No

Boot into the command line console in Ubuntu 16.04

As I just upgraded my 14.04 installation to 16.04, it booted right up to lightdm.

I had it properly setup to boot in a console before, but somehow it changed the behavior on me.

This is because the computer is now using systemd to boot.

I already had the GRUB variables setup as expected:

GRUB_CMDLINE_LINUX_DEFAULT="text"
GRUB_CMDLINE_LINUX="text"
GRUB_TERMINAL=console

But this is not enough if you want to start in the console when running systemd (which is running since 15.04).

systemd has a list of variables you can tweak using the systemctl command. To boot in ...

Start remote process on my X11 computer without encryption, how do I do that?

Running X Tool from a Remote Connection

I have been using SSH to connect to my LAN network computers and make all sorts of changes to the machines running in a console and X tools. Works just fine.

Setup the SSH Tunnel

I actually setup the X set with two things:

1) setup the SSH server with:

X11Forwarding yes
X11DisplayOffset 10

Then restart the SSH server.

2) setup your client with a ~/.ssh/config file where you enter:

Host remote
  ForwardX11 yes

This is the equivalent to the -X command line option, without you having to remember to enter the option every ...

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