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Display IP : Count of failed login attempts
The lastb command presents you with the history of failed login attempts (stored in /var/log/btmp). The reference file is read/write by root only by default. This can be quite an exhaustive list with lots of bots hammering away at your machine. Sometimes it is more important to see the scale of things, or in this case the volume of failed logins tied to each source IP. The awk statement determines if the 3rd element is an IP address, and if so increments the running count of failed login attempts associated with it. When done it prints the IP and count. The sort statement sorts numerically (-n) by column 3 (-k 3), so you can see the most aggressive sources of login attempts. Note that the ':' character is the 2nd column, and that the -n and -k can be combined to -nk. Please be aware that the btmp file will contain every instance of a failed login unless explicitly rolled over. It should be safe to delete/archive this file after you've processed it.

Dump HTTP header using wget
Let me suggest using wget for obtaining the HTTP header only as the last resort because it generates considerable textual overhead. The first ellipsis of the sample output stands for Spider mode enabled. Check if remote file exists. --2009-03-31 20:42:46-- http://www.example.com/ Resolving www.example.com... 208.77.188.166 Connecting to www.example.com|208.77.188.166|:80... connected. HTTP request sent, awaiting response... and the second one looks for Length: 438 [text/html] Remote file exists and could contain further links, but recursion is disabled -- not retrieving.

Backup files incremental with rsync to a NTFS-Partition
This will backup the _contents_ of /media/SOURCE to /media/TARGET where TARGET is formatted with ntfs. The --modify-window lets rsync ignore the less accurate timestamps of NTFS.

Watch for when your web server returns
If your web server is down, this command will periodically attempt to connect to it. If the output is blank, your server is not yet up. If you see HTML, your server is up. Obviously, you need to replace the Google URL with your web server URL... * 'watch' -- a command for re-executing a command and displaying the output * '-n 15' -- tells watch to redo the command every 15 seconds * 'curl' -- a handy utility for getting the source of a web page * '-s' -- tells curl to be silent about failing * '--connect-timeout 10' -- Try to connect for 10 seconds

list block devices
Shows all block devices in a tree with descruptions of what they are.

Anti DDOS
Takes IP from web logs and pipes to iptables, use grep to white list IPs.. use if a particular file is getting requested by many different addresses. Sure, its already down pipe and you bandwidth may suffer but that isnt the concern. This one liner saved me from all the traffic hitting the server a second time, reconfigure your system so your system will work like blog-post-1.php or the similar so legitimate users can continue working while the botnet kills itself.

See where a shortened url takes you before click

Show 'Hardware path'-style tree of all devices in Linux

Find the package that installed a command

Check SATA link speed.
Check SATA controller type. 6.0 Gbps - SATA III 3.0 Gbps - SATA II 1.5 Gbps - SATA I


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