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How can I determine the size of a directory or folder in Linux?

du -hs /path/to/directory -h: human-readable -s: summary (don't show size of each individual file within the...

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Tutorial: How to use Linux Screen

A problem that often arises when you’re dealing with lots of data is that it takes forever to process. So you SSH into your Amazon EC2 machine,...

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How to password-protect a PDF file on Ubuntu

In a terminal, type: sudo apt-get install pdftk Then, to add a password to a PDF file, type: pdftk <input-file> output...

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Can’t restart Apache in Ubuntu

When I try to restart Apache using the command: sudo apachectl -k restart I get this error: apache2: Could not reliably determine the server’s...