Update to PHP 5.6 on CentOS 6 using remi repository

With CentOS being a conservative distribution, security patches are still applied to CentOS 6, but no new versions are available. When running some websites – like Virtualmin – on CentOS 6, the old PHP version 5.3.3 can cause problems. Updating to a newer … Continue reading

Posted in PHP, Web technologies | Tagged , , | Comments Off on Update to PHP 5.6 on CentOS 6 using remi repository

Permanently reject a specific email sender address using postfix

Postfix generally accepts all sender addresses. It might be needed in some rare cases to reject one sender addresses for some reason. With postfix, there is the possibility to use the “check_sender_access” to set individual actions per sender address. For the … Continue reading

Posted in Linux Administration, Mailserver | Tagged , , , , , , | Comments Off on Permanently reject a specific email sender address using postfix

Certificate Transparency and unauthorized certificates

I own a domain which was bought a few months back which is managed by CloudFlare’s service in DNS-only mode. As I intended to only use CloudFlare’s DNS service, I disabled every option except the DNS related features. You can imagin the surprise to see certificates issued for my domain without my knowledge. Continue reading

Posted in Security, Web technologies | Tagged , , , , , | Comments Off on Certificate Transparency and unauthorized certificates

How to get scrollbar arrows in Linux Mint 17

Linux Mint is missing the scrollbar arrow buttons at the end of the scrollbars. There are situations in which those buttons can be very useful. This how-to will explain how to get them back. Sadly I could not find any … Continue reading

Posted in Linux Administration | Tagged , , , , , | Comments Off on How to get scrollbar arrows in Linux Mint 17

Verifying SSH configuration with a scan

Managing a number of Linux servers and keeping them secure can be a challenge. Certain tools can make the life of an admin a lot easier. To ensure an ssh daemon complies with a desired security configuration the admin can use a scanner … Continue reading

Posted in Linux Administration, Security | Tagged , , , | Comments Off on Verifying SSH configuration with a scan

Debug SSH Connection issue in key exchange

Securing a server means hardening the SSH server settings, but doing so can also cause issues with ssh clients. Finding the cipher or algorithm causing a failled connection can be tricky. Depending on the client used, the error message might be very … Continue reading

Posted in Linux Administration, Security | Tagged , , , , | Comments Off on Debug SSH Connection issue in key exchange

Automount a luks encrypted volume on system start

Linux supports encrypted volumes with luks. When a luks encrypted volume is set up during installation to be booted from, the volume is already configured and set up. When an encrypted volume is set up afterwards, the volume remains locked until … Continue reading

Posted in Linux Administration, Security | Tagged , , , , , , | Comments Off on Automount a luks encrypted volume on system start

Review: The perfect duo – powerbank and solar charger

Do you live in a sunny country? Want to use the sun’s energy to charge your mobile devices? This duo of a solar charger and a USB powerbank will let you harvest the sun and charge your devices whenever you … Continue reading

Posted in Uncategorized | Comments Off on Review: The perfect duo – powerbank and solar charger

Harden SSH server settings

Many Linux Administrators use ssh on a daily basis. Many of the ssh servers are in their default configuration. Not changing the default configuration puts the security of the server at risk. That is why it is important to follow a few … Continue reading

Posted in Linux Administration, Security | Tagged , , , | Comments Off on Harden SSH server settings

Manage photo EXIF data via terminal

Additional to the GUI tools that are available to manage EXIF information in photos, there are also command line tools that can do this as well. Command line utilities allow you to script the processing of photos. The following shows … Continue reading

Posted in Photo | Tagged , , , , , | Comments Off on Manage photo EXIF data via terminal