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A common way to "block" a website (eg, to eliminate it as a distraction) is to edit /etc/hosts and point the domain to the loopback address. Eg:

# Stop goofing off youtube.com

On Mavericks, I find that changes like this are seemingly ignored by the OS; after editing the file (with sudo) and saving, the site that should be blocked still loads.

I've tried resetting my DNS cache as follows:

dscacheutil -flushcache
sudo killall -HUP mDNSResponder

But the site still loads.

How can I get OSX Mavericks to notice a change to /etc/hosts?

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Could it be that it's the browser DNS cache that is not flushed? What IP does ping youtube.com use? –  Leonid Shevtsov Feb 18 at 14:32
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2 Answers

up vote 7 down vote accepted

According to the the hosts(5) manual page, the /etc/hosts file is used by mDNSResponder. Your attempts are correctly flushing the computer wide cache but you also need to flush the browser's private cache.

After each edit of /etc/hosts reset the mDNSResponder cache using this Apple technical note, OS X: How to reset the DNS cache:

sudo dscacheutil -flushcache

After doing this, reset your browser caches:

  • Safari: use the menu item Safari > Reset Safari.
  • Chrome: use the menu item Chrome > Clear Browsing Data.
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This fixed it. Under Chrome's "Clear Browsing Data", there are checkboxes for types of data. "Empty the cache" is the relevant one. –  Nathan Long Feb 18 at 15:34
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Delete your browsers cache and add www.youtube.com to your host file.

youtube.com resolves to www.youtube.com. Your browser is caching that information and redirects you to the www-page.

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