Who is a very used command, and, as most of us know, is a command to find out who’s working on your system.). But the who command can do much more then showing who is logged on. On his blog, Mike presents 4 options to use with who that “make it a great troubleshooting and statistics gathering command”. These options are:
who –r : Prints the current runlevel
who –b : Prints the system boot time
who –t : Prints out the last time the System Clock was changed
who –d : Prints out a list of all the dead processes on your system
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