crontab basics

How to list, create, edit and delete cron jobs.  Also describes crontab fields.
Added output of crontab command to file
Changed markdown syntax
cat basics

Includes: to standard output, to another file, and combining files
Fixed typo.  I think it was supposed to be "extracting data", not "estracting data"
Moves datacenter topics to a subdirectory
Clarified the purpose of each layer of the OSI model.
Monospaced commands and file paths per @avleen's suggestion
Removed double spaces between sentences and limited lines to 80 characters.
Bit of a hodge-podge commit.  Made changes per all but one of the remaining suggestions.
Pedantic typo correction
Add a pro tip section & a (hopefully) helpful tip
initial text for signals
Made some grammatical fixes and added terms to glossary.
updated soft skills section
updated soft skills section
updated soft skills section
Describe what it's like to work for a consultancy.

This is indeed personal experience, and covers many of the challenges
I've faced on the job on a daily basis.
Small style fix: day-to-day
updated soft skills section