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commandlinefu.com is the place to record those command-line gems that you return to again and again.

Delete that bloated snippets file you've been using and share your personal repository with the world. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

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May 19, 2015 - A Look At The New Commandlinefu
I've put together a short writeup on what kind of newness you can expect from the next iteration of clfu. Check it out here.
March 2, 2015 - New Management
I'm Jon, I'll be maintaining and improving clfu. Thanks to David for building such a great resource!

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Psst. Open beta.

Wow, didn't really expect you to read this far down. The latest iteration of the site is in open beta. It's a gentle open beta-- not in prime-time just yet. It's being hosted over at UpGuard (link) and you are more than welcome to give it a shot. Couple things:

  • » The open beta is running a copy of the database that will not carry over to the final version. Don't post anything you don't mind losing.
  • » If you wish to use your user account, you will probably need to reset your password.
Your feedback is appreciated via the form on the beta page. Thanks! -Jon & CLFU Team

Check for login failures and summarize

Terminal - Check for login failures and summarize
zgrep "Failed password" /var/log/auth.log* | awk '{print $9}' | sort | uniq -c | sort -nr | less
2009-03-03 13:45:56
User: dbart
Functions: awk sort uniq zgrep
Check for login failures and summarize

This command checks for the number of times when someone has tried to login to your server and failed. If there are a lot, then that user is being targeted on your system and you might want to make sure that user either has remote logins disabled, or has a strong password, or both. If your output has an "invalid" line, it is a summary of all logins from users that don't exist on your system.


There are 4 alternatives - vote for the best!

Terminal - Alternatives

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What others think

apt-get install denyhosts # for the win

Comment by linuxrawkstar 398 weeks and 5 days ago

if you want to see the list of invalid users attempted login against your system

zgrep "Invalid user" /var/log/auth.log* | awk '{print $8}' | sort | uniq -c | sort -nr | less
Comment by starchox 398 weeks and 4 days ago

That's a lot of pipes.

Comment by Buzzcp 360 weeks and 3 days ago

@starchox, even better:

zgrep "Invalid user" /var/log/auth.log* | awk '{print $8 " " $10}' | sort | uniq -c | sort -nr | less
Comment by Buzzcp 360 weeks and 3 days ago

Your point of view

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