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For quick validation of folder's file-contents (structure not taken into account) - I use it mostly to check if two folders' contents are the same.
This command does a tally of concurrent active connections from single IPs and prints out those IPs that have the most active concurrent connections. VERY useful in determining the source of a DoS or DDoS attack.
Useful to detect which process is causing system loads. It shows process PID so as we can take further actions.
Very useful for finding the largest files and subdirectories at any given point. Any user can run it from current location just when need to know their largest files and subtdirectories from a certain point down as well.
This will tell you who has the most Apache connections by IP (replace IPHERE with the actual IP you wish to check). Or if you wish, remove | grep -c IPHERE for the full list.
List top 20 IP from which TCP connection is in SYN_RECV state.
Useful on web servers to detect a syn flood attack.
Replace SYN_ with ESTA to find established connections
usefull in case of abuser/DoS attacks.
find -printf '%u\n' | sort | uniq #just users
find -printf '%g\n' | sort | uniq #just groups
Sort IP address by order
The description of how the one-liner works is here at my blog:
Greps IRC logs for phrases and lists users who said them.
shows all RPMs with files in the current directory & its subdirectories.
Ever use 'locate' to find a common phrase in a filename or directory name? Often you'll get a huge list of matches, many of which are redundant, and typically the results are not sorted. This command will 'locate' your search phrase, then show you a sorted list of just the relevant directories, with no duplications. So, for example, maybe you have installed several versions of the java jre and you want to track down every directory where files matching "java" might exist. Well, a 'locate java' is likely to return a huge list with many repeated directories since many files in one directory could contain the phrase "java". This command will whittle down the results to a minimal list of unique directory names where your search phrase finds a match.