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Sometimes my /var/cache/pacman/pkg directory gets quite big in size. If that happens I run this command to remove old package files. Packages that we're upgraded in last N days are kept in case you are forced to downgrade a specific package. The command is obviously Arch Linux related.
Kill all processes belonging to a user, with a minimum of resource usage. Great for the times when a user fork-bombs the system and it's difficult to login or run commands.
In OSX you would have to make sure that you "sudo -s" your way to happiness since it will give a few "Permission denied" errors before finally spitting out the results. In OSX the directory structure has to start with the "Users" Directory then it will recursively perform the operation.
Your Lord and master,
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.
In case you ever got to many arguments using rm to delete multiple files matching a pattern this will help you
The keycodes are a result of pressing:
Remove old kernels (*-generic and *-generic-pae) via apt-get on debian/ubuntu based systems. Tested on ubuntu 10.04 - 12.04.
ssh port forwading
Flush the DNS cache under Ubuntu (Debian?)
suspicious/anomalous ownership may indicate system breach; should return no results
Find installed network devices.
Can use minute - m, hour - h
Eg: sudo bash -c "sleep 2h; pm-hibernate"
will hibernate the system after 2hours.
Purges DNS cache of OS X.
dscacheutil -flushcache does not work since OS X 10.7.
">>" appends to the file
">" replaces the entire file
make sure to use ">>"