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  • Sep 16 / 2016
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Linux

Renew a GPG key when you get “GPG error – KEYEXPIRED”

Getting this error when trying to update packages on your linux distro using apt?

This just means that the GPG key is expired and that you need to renew it.

You can list expired keys and get the ID by using this command:

Here, we can see that ID “4BD6EC30” is expired and is leading to the issue.

Let’s now update this key:

And you can now perform the update properly, you won’t get error anymore.

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  • Sep 07 / 2016
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Linux

Send an UDP packet with NetCat

It can be needed to test an UDP connection with a server to ensure that connectivity is working and double check the data received.

Let’s take a simple example with a remote logstash server:
– Server mylogstash.mydomain.local
– Listening on port 5000

On emitter side, we are sending an UDP packet simulating a log line coming from an application:

On receiving server side, we are executing a tcpdump to check that packet is correctly coming with good content:

Here we are! It’s very simple to control UDP flows or simply check connection between 2 servers.

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  • Aug 22 / 2016
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Linux

Find and identify where inodes are used

Your monitoring system is claiming that your server is running out of free inodes but your disks are not full at all? Maybe you just need to check your filesystem usage and how many files are being used at the same time… Here are some tips to check and identify the inodes being used.

First of all, you can check percentage of inodes used with this simple command:

You will see inode usage for your partitions and mouting points:

Here, we can easily see that /var is using 83% of inodes, which is quite high.

Let’s now identify how those inodes are used with a compound command using find:

You will get a sorted result like this (I truncated to display only the last lines which are the most important):

We can clearly see that inodes are mostly used by /var/spool/postfix/maildrop. You just have to go in that folder and check if files are useful and/or if you can do some cleaning there.
Then, once files are removed and directory clean, your inodes will be freed and everything will be back to normal!

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  • Aug 11 / 2016
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Database

Calculate Database/Table size in MySQL

MySQL is an open-source relational database management system (RDBMS) available under the terms of the GNU General Public License, as well as under a variety of proprietary agreements.

Thanks to some few functions, it’s possible to retrieve important information about database size and/or table size for a MySQL instance.

Size for all databases

Size of tables for a specific database

For a complete documentation, please refer to the official documentation on their website https://www.mysql.com

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  • Aug 02 / 2016
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Linux

Skype group chat not working on linux

With Linux version for Skype, it can happen that group conversation are not working as expected (conversations do not start, or updates are not working, or group members do not appear, …).

You can check MSNP version you are using by typing this command in any conversation chat:

If you are getting this message (“LoggedOut”), this means that you have the MSNP issue:

You can so enter in the chat:

Then, restart Skype.

Once restarted, you can check again the MSNP version:

You should now get “LoggedIn”:

Et voila, Skype will now work correctly 🙂

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  • Jul 21 / 2016
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Linux

Open bash session into a docker container

Once a docker container is started, it’s always hard to get access into and see what’s happening inside. As a workaround, the easiest way to understand what’s happening in a container is to get a CLI on it and investigate.

Since version 1.3, you can easily open a bash session into a running container by using:

  • The ID of the container:
  • Or the name of the container:

You will get access with a bash session to your container:

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