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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:

select() returns immediately instead of waiting for timeout

The select() Unix command allows you to wait on an event on a set of file descriptions, in most cases, sockets.

The select() function accepts the following parameters:

Largest file descriptor + 1
An fd_set of file descriptors to listen to for read
An fd_set of file descriptors to listen to for write
An fd_set of file descriptors to listen to for special events (i.e. closed on the other end)
A timeout structure

The fd_set pointers are all optional. Actually, if all are set to NULL, select() waits for the specified timeout and then returns. Similarly, the ...

One thing that I find annoying in gvim is the foldcolumn parameter which is not reset once you are done with a diff process.

Of course, gVIM does not really know when you are done diff-ing, so its behavior makes sense... only it is still annoying.

To remove the fold (2 gray columns on the left used to hide areas that match in each file) you simply have to set the foldcolumn parameter to zero:

:set foldcolumn=0

Just in case, you enter a diff from within vim by loading two files, then using;

:diffsplit #

The diffsplit can specify any buffer number, I use the # as the other buffer (the ...

HTML background that fits the screen

You can actually define an image or a background (with CSS) that fits the area in which is it shown.

For a simple image use a width of 100%, then the browser computes the height for you.

  <div class="header"><img src="images/background.png" width="100%"></div>

This code will make the image width match the width of the <div> tag. Assuming the <div> tag fits the screen width, it will show in the full width, stretching as required.

When trying to do that with a background image in CSS, you want to use the background-size parameter ...

Useful online network tools

I'm starting this page and hope to think about it again at a later time when I find additional tools... but as I have network problems I often need these types of services to make sure I can get the information I need.

For more Network stuff, click on the Network tag!

What is your IP address?

Check your current IP address from your browser:

http://alexis.m2osw.com/nvg510/my-ip.php [Super clean version!]

https://www.whatismyip.com/ [More advance and with ads...]

What is my DNS?

This one is for people who setup a DNS to make sure that it can accessed from all over the world. It ...

Working on a PHP application setup, I stumble upon a problem. Going to the installation page, I got the dreadful error:

Forbidden

You don't have permission to access <root-path>/admin/install on this server.

Looking at the error logs, the only thing reported was:

client denied by server configuration

The fact is that Apache does not tell you which setting actually forbids the access. I guess that's because once it gets checked by Apache, it is a blend of all the settings and not a tree being followed.

Looking a round, and since I already had that error not too long ...

I work with Apache a lot. It is a really good web server that has many options and features. Unfortunately, maybe it has too many of them!

I ran in a problem where a notification from one server to another would fail with the following error:

[Fri Oct 11 19:43:50 2013] [error] [client 162.226.130.121] client denied by server configuration: <path to file>

Looking at the error, I was first thinking that my script was generating the error. The fact is that my script does not generate error 403. It has a 400 and 500 but not 403.

So looking at the error I thought, maybe that's an ...

Full Update

Once in a while, I update my policy file because tripwire tends to checks EVERYTHING and many things are being updated on a constant basis (such as the letsencrypt files which appear under /etc/letsencrypt/..., which should use /var/lib/letsencrypt/..., but I digress here...)

So as a result I have to update the file and to do so I edit my twpol.txt file and then run the following three commands to update the database:

sudo twadmin --create-polfile --cfgfile tw.cfg --site-keyfile site.key twpol.txt
sudo rm /var/lib/tripwire/hostname.twd
sudo tripwire --init

The ...

My syslog was filled up with errors such as this one:

    Sep 27 00:58:42 halk postfix/error[16751]: 628254C02F0: to=<mo_fax@m2osw.com>,
    relay=none, delay=1.8, delays=0.06/1.6/0/0.14, dsn=4.4.1, status=deferred
    (delivery temporarily suspended: connect to mail.m2osw.com[69.55.231.156]:25:
    Connection timed out)

I've been wordering for a while, since I can use Thunderbird with a direct connection to my server, I was not too concerned, but tonight I really needed to support those emails because I have work to do that requires it.

Got NVG510 to setup?
Hacking my ...

Ubuntu 12.04 to 12.10

I just upgraded from 12.04 to 12.10 and my desktop was fully reset to the defaults. Rather annoying.

The worst part is that I tried to do things such as reassigning the Alt-F1 and Alt-F2 keys and it did not work. Somehow the default Gnome keys remained in effect!

I found the solution on Ask Ubuntu.

gsettings set org.gnome.desktop.wm.keybindings panel-main-menu "[]" # disable Alt+F1
gsettings set org.gnome.desktop.wm.keybindings panel-run-dialog "[]" # disable Alt-F2

Editing the preferences did not work at all.

Source: ...

Brdige between your Host and Guest computers

I use VirtualBox and had a problem with copying files between my host (main computer on which you boot your computer) and the guests (virtual computer that you run on your host).

The fact is that it is all explained right here:

https://www.virtualbox.org/manual/ch04.html

There are a few steps as follow.

Using scp

Here, I have an example of GParted where I could not install the VirtualBox tools as mentioned below. This is mainly a matter if setting up an SSH server and allowing connections for a given user.

Install the VirtualBox Tools

Install the Virtual Box Tools ...

Unfreeze your Mouse when it Froze

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Main Menu

Welcome to The Linux Page

What is your IP address?

What is my DNS?

Forbidden

Full Update

Using scp

Install the VirtualBox Tools