Category: Linux
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How to identify the process listening on a port
This is mostly for own use, but: If you’ve ever had a server which netstat showed was listening on one or more ports you weren’t expecting, you can use this command to find out which process is listening there: fuser -vn tcp 4444 Which in this case happens to be owned by JBoss, and not…
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How to block an IP in Linux
I run Debian on my server, and I often find that my server is being attacked by other computers. Brute force SSH attacks, viruses scanning for the ability to spread, things like that. I’ll go into the SSH brute force defenses in a later post, but for now I’ll cover how to easily block an…
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How to cleanout your postfix queues by sender
This post is mostly to help me remember how to do this, if the situation arises again. I just had a lot of mail backup on my server. The 10MinuteMail inbox was over 300 MB (usually it kept below a megabyte), Postfix’s active queue was maxed out at 20,003 entries (why the 3, I don’t…