I put a cronjob in /etc/cron.{hourly,daily,weekly,monthly} and it does not run and how can I troubleshoot it?

Posted on in Categories Cloud Computing, Howto, Open Source, Web Developer last updated August 27, 2017


Recently I created a simple shell script called backup.sh in /root/scripts directory to just backup MySQL database and dumped it to /nfs/mysql/ directory. I put a file (more like used the ln command to create a soft link ) in /etc/cron.hourly/ and it doesn’t run. There was no error in systemd log or cron log. Why is my cron job was not working, and here is how I troubleshoot it.

Linux/Unix desktop fun: Bastet Tetris(r) clone with block-choosing AI for console

Posted on in Categories Linux Games, Open Source last updated August 18, 2017

Xkcd - hell
Do you love the puzzle and Linux/Unix-like system? Command line? Try ncurses based Tetris clone which is harder than every other Tetris out there. From the project home page:

Have you ever thought Tetris(R) was evil because it wouldn’t send you that straight “I” brick you needed in order to clear four rows at the same time? Well Tetris(R) probably isn’t evil, but Bastet certainly is. >:-) Bastet stands for “bastard tetris”, and is a simple ncurses-based Tetris(R) clone for Linux. Unlike normal Tetris(R), however, Bastet does not choose your next brick at random. Instead, Bastet uses a special algorithm designed to choose the worst brick possible. As you can imagine, playing Bastet can be a very frustrating experience!

OpenSSL drops TLS 1.0/1.1 support for Debian Unstable and what does it mean for Debian sid users?

Posted on in Categories Debian Linux last updated August 7, 2017

From the announcement mailing list:

I’ve just uploaded a version of OpenSSL to unstable that disables the TLS 1.0 and 1.1 protocol. This currently leaves TLS 1.2 as the only supported SSL/TLS protocol version.

This will likely break certain things that for whatever reason still don’t support TLS 1.2. I strongly suggest that if it’s not supported that you add support for it, or get the other side to add support for it.

OpenSSL made a release 5 years ago that supported TLS 1.2. The current support of the server side seems to be around 90%. I hope that by the time Buster releases the support for TLS 1.2 will be high enough that I don’t need to enable them again.

Increase your Linux server Internet speed with TCP BBR congestion control

Posted on in Categories Cloud Computing last updated July 22, 2017

I recently read that TCP BBR has significantly increased throughput and reduced latency for connections on Google’s internal backbone networks and google.com and YouTube Web servers throughput by 4 percent on average globally – and by more than 14 percent in some countries. The TCP BBR patch needs to be applied to the Linux kernel. The first public release of BBR was here, in September 2016. The patch is available to any one to download and install. Another option is using Google Cloud Platform (GCP). GCP by default turned on to use a cutting-edge new congestion control algorithm named TCP BBR.

Why port 80 (HTTP) reported as open by nmap when it is closed?

Posted on in Categories Security last updated July 2, 2017

Why are some ports reported as open by nmap?
I recently setup a small server which is running Debian 9. The purpose of this machine is to run OpenVPN server on port 443 to bypass censorship. It runs the following services and nothing else:

  1. Squid on private IP belongs to VPN pool (10.8.0.1:3128)
  2. SSH on private IP belongs to VPN pool (10.8.0.1:22)
  3. DNS resolver on private IP belongs to VPN pool (10.8.0.1:53)
  4. OpneVPN on public IP port 443 (server_public_ip_address:443)

Download of The Day: Debian Linux 9 ( Stretch )

Posted on in Categories Linux News last updated December 1, 2017

Debian GNU/Linux version 9.0 stretch has been released ( jump to download ) after many months of constant development and available for download in various media format. Debian 9.0 is a free operating system includes various new features such as support for mips64el architecture, GNOME 3.22, KDE Plasma 5.8, LXDE, LXQt 0.11, MATE 1.16, Xfce 4.12, Linux kernel 4.9 and more. Debian 9 is dedicated to the project’s founder Ian Murdock, who passed away on 28 December 2015.
Debian 8.x 64-bit-mate-desktop-screenshot