The Linux Page

network

stream_socket_client() fails with no errors...

Today I had a weird one.

The PHP function named stream_socket_client(), used to create a socket to communicate with another computer over a network, may return $errno = 0 and $errstr = "".

The PHP reference actually mentions the problem:

On failure the errno and errstr arguments will be populated with the actual system level error that occurred in the system-level connect() call. If the value returned in errno is 0 and the function returned FALSE, it is an indication that the error occurred before the connect() call. This is most likely due to a problem initializing the socket. ...

How to setup a Linux firewall

Introduction

If you setup a Linux box, you want to setup a firewall before you connect your computer to the Internet. If you are setting up a remote server, it should only have the SSH port open. Connect to it, setup the fire, then only install the other servers and open ports as required (and only ports that need to be connected from the outside.)

Any port that you open without the firewall already setup is at risk. You may want to install PHP and along will come a database which may open a port to the Internet. Something that you just don't want to happen.

Setup Firewall

To ...

Cannot connect my Host system to Cassandra running on my Guest VM

I found a different way which is to use the:
Local Network or Host-only Network on your Virtual Machine

Today I did my first full install of Snap on a VM in my Ubuntu development system that runs VirtualBox.

This took me about 1h between getting all the files ready from our own APT repository, and then finding out all the setups needed (we have a few working installations, but we added all the necessary magic with time and did not clearly document all the steps yet... argh! so much to do!)

At some point, I wanted to setup the "domains" and "websites" tables on the VM. ...

Bad move for PHP unpack()! So unpack() stopped working?

Today I noticed many errors on one of my websites. Looking closer into it, I noticed that the code for the mo_references Drupal module stopped working.

It took me some time, especially because the code seemed to work just fine as all the files could easily be displayed.

Actually, that was not the case. The unpack() character 'a', which I used, was transformed from a simple string that gets trimmed, to all the characters, including the NULL characters. Ouch! Now we have to use the 'Z' character instead.

I use it to unpack() a tar file by loading 512 bytes of data in a ...

HP Printer options not offering "Color: Off" option anymore

As I upgraded to Ubuntu 13.10, I noticed that I lost the option to turn off the color when printing.

Looking around all the available options, no one to make it black and white (although the old option was saying something like: Color: Off; it was somewhat weird.)

Now that option is completely gone. There is no way for me to turn off my HP Printer color when I am in Acrobate or LibreOffice. I searched on the Internet to see whether that was just HP trying to get you to use colors on your printer or whether the option was available... somewhere else.

Indeed, I had to go to the System ...

My NVG 510 broadband light is blinking red

Somehow my NVG 510 broadband light started blinking red a couple of time in the last few days. I've been wondering why and I think I have the answer now.

In most cases it may just be that the broadband signal disappears for too long and the modem disconnects.

However, in my case, I think it was because they made an upgrade (a push!) on the modem because a few things do not work as expected anymore. (i.e. I cannot access the nsh shell anymore...)

Whenever software is upgraded, the likelyhood that you have to reset the whole thing is very high. I had to restart twice and even after that, ...

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 ...

Postfix says it does not allow relaying?!

As we are upgrading our server to jump from version 12.04 to 13.04, we encounter a few problems.

Two with Postfix, first the Postgrey port has changed. It was 60000 before, now it is 10023. Don't ask me... Anyway, that was the easy one.

The other problem was a relay error. I could send emails all I wanted, but not my partner who does not show his server as part of our Made to Order Software Corp. network. Relay is why a computer allows emails from server X to be sent to server Y through server Z. You are server Z, that's the relay.

The fact is that if you can log in your account on ...

Setting up my home server with the NVG510 router on AT&T Uverse

My Rant

I got a new router as AT&T forced me to a new product called U-Verse. They are actually forcing all their users to switch to that new systems as the new optic cables are now installed and they probably have a goal to turn off their old infrastructure soon.

The old router I had would generate a gateway on their side. The router was just a router ...

Creating a drive mirror with LVM, including exact partition cloning

LVM today can create a mirror of your data without having the need for mdraid (or hardware raid).

Problem is, I did not find any documentation that makes sense and there doesn't seem to be a graphical interface that can help you with that (at least not under Ubuntu Gnome.)

So... I decided to spend the time because that's probably less time anyway than trying to create and maintain and md device.

The fact is, it is rather simple, but requires quite a bit of knowledge.

Copying the Partitions Exactly

First, I wanted the partitions to be exactly the same and using fdisk did not ...

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    Enhanced Dynamic Link Library--an enhanced dynamic linker that simulates the behavior of the Linux and other Unix linkers by offering a way for libraries to link back inside the main executable. See the EDLL website for more information.
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