The Linux Page

Help other users realize that everything is possible, especially avoiding Windows for their own personal use.

Welcome to The Linux Page


Fox Trot by Bill Amend. Click to enlarge.
Click to enlarge

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:

Embedded videos from YouTube.com used to work just fine on my website.

Today, though, I just noticed that my video was not showing up on one of my pages. Looking into it, I found out that the problem was the protocol.

I'm not too sure whether it was my browser or YouTube,com (although I'm not too sure how YouTube.com would know...) but the fact is that the iframe source was using HTTP and the page I was viewing used HTTPS.

By editing the page and changing the YouTube.com video from HTTP to HTTPS resolved the issue. It is generally much better to always use encryption anyway.

I have a table with a few columns, two of which are integers, one of which can be NULL in which case the other integer is to be used in my query.

CREATE TABLE my_table (col1 INTEGER NOT NULL, col2 INTEGER);

If `col2` is NULL, then use `col1`. As is, there is how my query looks like:

SELECT MIN(IF(col2, col2, col1)) AS smallest FROM my_table LIMIT 1;

In other words, I need to get the row with the smallest integer, but if one column is NULL, I want to use the other column value.

On a very small sample, the query is still very fast, but the real version is not unlikely to have thousands ...

Today I noticed that my fail2ban wasn't running.

Looking into it, I could see that an error was happening on startup. This pretty much always mean that something's wrong in the configuration files.

sudo systemctl start fail2ban
Job for fail2ban.service failed because the control process exited with error code.
See "systemctl status fail2ban.service" and "journalctl -xe" for details.

However, somehow, systemd would not show me the error with the status or checking the journal and it would not write anything to the /var/log/fail2ban.log file which stayed ...

I have been using Thunderbird for a long time and yet I still did not know about the Compact feature.

A while back, i would use my Local Folders to save Junk, Draft, and Sent emails. This is really fast by default. But at some point I had a problem and reverted to using the remote folders which worked.

The problem was that Thunderbird would tell me that my Local Folders were full even though looking at them they were clearly empty.

The way this works is really annoyingly bad:

1. it accepts emails in a file, like the good old days, it uses one file for any number of emails

2. it adds new ...

Lately, I received emails from a customer something like 12 hours later...

So I checked closer and could see that the email was from hotmail.com.

Great.

On the server, I edited my whitelist to see what was going on:

vim /etc/postgrey/whitelist_clients.local

Searching the list I could see hotmail.com, so why is it that it gets bounced with a 450 by Postgrey if it is whitelisted?

Looking closer at the logs left behind by Postgrey, I found this line:

Apr 23 06:33:34 m2osw postgrey[1742]: action=greylist,
      reason=new,
      client_name=<secret>.outlook.com,
      ...

As I wanted to use SugarCRM on my new server, I looked into the Community Edition and apparently the company is not willing to convert their code so it works under PHP 7.

So that would not work on a newer system because the code uses quite a few forbidden mechanism (wrong class definitions, old defunct functions...) and that prevents to even instal the system on your machine.

Now, I have looked closer into it and I am getting a version that works pretty darn well already. I still have some issues here and there, but I think you can already make use of that version. Except for one thing which ...

In my development, once of the steps is to check the changes I made before I commit them.

To do so, I often use Meld.

Unfortunately, the preferences disappeared and it makes things harder to tweak large changes!

The fact is that my brain does not correctly support the Macintosh like Menu at the very top. (It's not just my brain, it's also the fact that when I move my mouse, it focuses windows automatically, which is the normal X-Windows behavior, and having the menus on the top is not acceptable in that case!)

You remove the menus at the top-right of the screen with:

sudo ...

The following command adds a rule to your iptable firewall:

iptables -A INPUT -p icmp --icmp-type 255 -j ACCEPT

As we can see, the rule accepts protocol ICMP and uses ICMP type 255. Only, if you look for a list of valid ICMP types, 255 is not included.

The fact is that this rule actually says: accept any ICMP type. If you changed the ACCEPT with DROP, it would refuse all ICMP packets. In most cases, it is safe to accept ICMP packets since they do not divulge more information than necessary.

Note that in your firewall script, you may use "any" instead of 255. That will make it ...

In Ubuntu 16.04, I wanted to add a user cron file with crontab -e, which has a new behavior: the very first time, it asks you what editor you want to use (i.e. nano, vim, ...)

If you choose the wrong one, then next time it does not ask you, it remembers your choice forever, so you'll be stuck.

The nano editor is okay, but difficult to work with if you're used to something like vim.

The data actually gets saved in a hidden file of your home directory named .selected_editor.

# Generated by /usr/bin/select-editor
SELECTED_EDITOR="/usr/bin/vim"

Mine was set to ...

Today we had a problem with a combo of website that we never tried to run together.

Looking into it, it was definitely a problem with SSL. However, Apache2 would tell us absolutely nothing about it. No error or access logs. I think this is because it would happen at the time Apache and the client negotiate the SSL connection and Apache does not report such problems (at least by default, it might in case you turn on some debug mode?)

We had two different settings for two websites using the snakeoil certificate (As we test on VM machines, we use the snakeoil certificate as an easy way to check ...

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