Smartkey - Java Software Consultancy » Other

Identifying which processes are using network ports on a Mac

Steve Neal — Thu, 09 Feb 2012 11:16:54 +0000

Typically I’d use netstat’s -o flag to identify the process ID when listing networking activity from a Linux/Unix machine. Unfortunately this option is not available with netstat on Mac OS X.

I recently has a rogue process (I suspected a virus) on my Mac that was creating thousands of connections out to hosting providers. Luckily I found this fix, which uses lsof to list the network files that are being held open instead. It works a treat:

~$ lsof -i -P

The -i flag restricts output to the networking files, the -P flag prevents well known port numbers from being converted from numbers to text (e.g. 80 -> http). Try it without the -P flag to see the protocol short names.

Using this command, I identified which process was creating the unwanted connections and to dealt with it.

Count the processors on a Linux server

Steve Neal — Thu, 02 Jun 2011 14:46:16 +0000

If you need to see how many processors there are available on a Linu/Unix server, use the following command from your shell:

cat /proc/cpuinfo | grep processor

each of the processors will be listed in the output. For example, on a server I use the output looks like this:

processor : 0 processor : 1 processor : 2 processor : 3 processor : 4 processor : 5 processor : 6 processor : 7

So, on this server we can see there are 8 processors available.

Deleting all files over a certain age on a Linux server

Steve Neal — Wed, 04 May 2011 15:38:58 +0000

To delete files on a Linux server that are all over 3 days old, use this:
find /log/ -type f -mtime -3 -exec rm {} \;
This command will find all files in /log over 3 days old and will run the rm command for each of them.