# What does “restricted \write18 enabled” mean and why does TexLive keep reporting it?

I've installed a backported version of TL2012 on Ubuntu 12.04, and every time I start pdftex, xetex, luatex, pdflatex, xelatex, or lualatex, I get the statement restricted \write18 enabled. entering extended mode. I don't recall seeing this in Miktex so I wonder whether I did something wrong during the installation. Interestingly, I don't get the message when I run tex.

First of all, what does it mean? Second, is it a normal message for Tex Live (2012)? Finally, if it is an error, how can I fix it?

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