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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!

  • 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

  • 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 🙂

  • 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:

  • Jun 09 / 2016
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Linux, Python

openssl/pyOpenSSL – “SSL23_GET_SERVER_HELLO:tlsv1 alert internal error”

You’re getting this annoying error message again and again when trying to fetch certificate and/or establish a connection to your website using openssl:

This issue is well known in several openssl versions, and a bug has been addressed for Ubuntu repositories:
https://bugs.launchpad.net/ubuntu/+source/openssl/+bug/1475228

For now, there’s a simple workaround that works to quickly fix it!

For openssl

If you’re facing it while using openssl directly, you can fix it by specifying the servername on command-line:

For pyOpenSSL

If you’re having this issue while using pyOpenSSL (python wrapper for OpenSSL), it can also be fixed with a quick workaround by adding the option set_tlsext_host_name() to specify the server name in your “Connection” object.
You will get something like this:

  • Jun 02 / 2016
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Linux

Configure VLan interface (with alias)

If you want to isolate multiple networks, you can use VLAN (Virtual LAN). On most of the switches, you can configure VLAN to handle tagged packets and be able to send them to a specific port by isolating it. A VLAN is assigned a specific id that can be any number between 1 and 4096.

Most of the Linux distributions can handle tagged packets and VLAN usage, but this feature is not mandatory enabled by default. For the example, I’ll present here how you can enable and configure VLAN on Ubuntu Server 14.04.

First, you need to install the vlan package:

Temporary configuration

Then, you should load the 8021q module into the kernel (guessing you’re using a recent and not customized kernel):

As it’s not possible to create a VLAN on virtual interface, you will have to use physical interface and alias to make it work. You can create additional interface with:

Then, you can assign an address to this interface:

And finally make the interface up:

Permanent configuration

You have to load the module automatically and permanently:

Finally, set the configuration in /etc/network/interfaces in order to make it loaded on startup:

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