RPM: List all installed packages by size

shell$ rpm -qa --queryformat '%10{SIZE}\t%{NAME}\n' | sort -k1,1n 

Enable “Subject:” logging in Postfix

Edit the Postfix’s main.cf file and add the following line (or uncomment it):

header_checks = regexp:/etc/postfix/header_checks

Create /etc/postfix/header_checks file and add the following line:

/^subject:/ WARN

Finally, reload/restart Postfix. From now on there will be a “warrning: header subject” in your maillog.

Quick Fix: Support for HiDPI in Caprine for Windows

In order to fix the wired looking (small) font of Caprine for Windows you just have to change (add) the “zoomFactor” parameter in ressources\app\index.js right after webPreferences:
zoomFactor: 1.2,


Save the file and re-run the app. The font should be readable now.

More about Caprine – https://github.com/sindresorhus/caprine

CentOS: Change default MTA (Mail Transfer Agent)

Here’s a simple way to change your default MTA on CentOS:

# alternatives --config mta

There are 2 programs which provide 'mta'.

  Selection    Command
*+ 1           /usr/sbin/sendmail.sendmail
   2           /usr/sbin/sendmail.ssmtp

Enter to keep the current selection[+], or type selection number: 2

# sendmail -V
sSMTP 2.61 (Not sendmail at all)

PIP – update all Python packages

pip freeze --local | grep -v '^\-e' | cut -d = -f 1  | xargs pip install -U

Windows 10 – God Mode

To activate God Mode, right-click the desktop and select New > Folder. Highlight this folder, press F2 and name it:


FIX: aws-cli – AWS was not able to validate the provided access credentials

Simply adjust / sync your server’s clock in case you get the following error message while using aws-cli – “AWS was not able to validate the provided access credentials”

Watch (online) Microsoft’s Windows 10 Event On January 21st

To watch the event online, head over to Microsoft’s Windows 10 page at 09:00 (PT), 12:00 (EST), 18:00 (GMT). Microsoft will most likely post up a VOD of the keynote afterwards, allowing anyone on catch-up.

CentOS: Clear cached memory

Use the following command to clear you cached memory:

root@linux [~]# echo 1 > /proc/sys/vm/drop_caches

clear cached memory

gem install rmagick – Can’t find Magick-config (CentOS 6)

In case you receive the mentioned error while trying to install rmagick then simply issue the following:

# yum install ImageMagick-devel

Once ImageMagick-devel is installed then you can retry installing rmagick using:

# gem install rmagick