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console

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 ...

Remove the Keyboard Repeat in a VirtualBox console running Linux?

When I use virtualbox over the network (from a headless computer) and I connect using SSH, that virtualbox is going to be slow.

Somehow, I did not have that problem with older versions (Ubuntu 14.04 and older) but newer versions have required me to turn off keyboard repetition otherwise I get keys repeated (mainly the Enter key when something takes processing time at the time I hit the enter key) as in:

Heeeeeelllllooooo

The solution is to run the folloing command:

setterm -repeat off

It works in most terminals, for sure, the regular Linux console you get after installing a server in a ...

Supermicro X9SCI/X9SCA, video is gone!

As I am still trying to get my computers to work with a dual seat (or multiseat), I did an attempt in using the onboard video (a relatively decent Matrox card.) So I went in the BIOS and changed the setup for the video from Offboard to Onboard. Big mistake!

The video stopped working. On reboot the computer beeped 8 times and booted the OS normally (I have SSH setup so I could access the computer, but absolutely no video on either port: on board and off board.)

I have a Supermicro X9SCI/X9SCA. Searching for "no video" or "missing video on boot"... returned nothing ...

[ODBC Driver Manager] Data source name not found and no default driver specified

As I was working on a MS-Windows installation, I ran in this weird error: Data source not found and no default driver specified...

This was output when I was running the following in a command line prompt:

osql -E

The result should have been an MSSQL prompt instead!

The problem on the computer was that I uninstalled MSSQL 2005 that was automatically installed by Visual Studio C++ and was not compatible with our application, so I first uninstalled that but that uninstallation is really not proper. It leaves a LOT of things behind.

After that I installed MSSQL 2014 which was reported as ...

Adding a group for to a logged in Linux user

Once in a while I want to add my user to a group and then right away make use of that group.

Unfortunately, in general Unix kind of forces you to re-log in for the new group to be attached to your account.

However, a command has been added, a while back, to do just that on the fly. Not something you would want to use in a script, but at least, it works for me when doing a few things here and there.

In my case, I wanted to run QEMU, which I hadn't done in a while, and the system told me that it could not open the KVM, the error: kvm permission denied.

The problem was that I was not part ...

The for() in C, C++, Java, PHP, JavaScript...

As I am working on my as2js compiler, I stumble on a couple of problems with the for() loop parsing because of the in keyword. That made me think and the for() statement was actually a very funny one. Yes! You can actually write something like this and it compiles:

int zero;
for(3;2;1) zero;

As you can see, all 3 entries in the for() statement are valid expressions and therefore the compiler can compile that code. This creates a loop that runs forever, similar to:

for(;;) zero;

but much less clear to read, obviously.

Now that's food for thought, isn't it?

In JavaScript, you ...

Repair a Cassandra Cluster

I use the Cassandra database cluster system to manage a new set of websites and once in a while I start getting many errors and the website stops working altogether.

When that happens, it is likely that Cassandra broke something in the temporary tables that it holds. The only way to go past that problem is to clear those tables. Until then, it will fail over and over again (they really would need some euristic to auto-clean up even if it means that you're losing some data.)

The command to repair the database, really quick, is as follow:

nodetool scrub snap_websites files

Note that ...

#PCDATA and DTDs

If you are like me and write DTDs to check your XML files to make sure you don't have too many mistakes in them, then you probably have had this problem before.

The #PCDATA has a very special behavior and it is really restrained as follow:

  • #PCDATA must appear at the start
  • #PCDATA must be repeated from zero to infinity, so only * work with it
  • #PCDATA cannot be used with sub-groups (things between parenthesis)

Something like this:

<!ELEMENT Z (P | (#PCDATA | A | B | C)* | Q)+>

does not work because you use + and #PCDATA is within a sub-group.

What you need ...

nvidia_XXX.ko No Such Device

Today I got a new video card because it looks like the old one I had was going bad. I hope that was not my KVM, although we'll see when it gets hot again, whether the video goes bouncy again or not... If not, then the old card is good for the trash (although it works in console mode just fine!)

So I got a new card. My old one was a NVidia GT 220. Fairly old model. Yes.

The new card is an NVidia GT 630 (to be precise: Asus GT630-SL-2GD3-L.)

When I tried to start X11, I saw an error (really quick) and the system did not come up. Looking closer into the matter, I could see that the NVidia ...

Console color: dark blue on black unreadable

As I work in consoles every now and then, I run in that one problem:

Some text is written in Dark Blue over the Black background:

This is a good example of what I'm talking about.

And if you can read that text, wow! (without selecting it first.

So... how could you change the color of that blue to make it readable? There is a way by sending some escape command to the console:

echo -e "\\e]R\\e]PC6495ed"

That command changes the color of the blue to a light blue (somewhat "cyan", although not light cyan.)

The "\\e]R" part is to reset the colors to ...

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