UNIX Environment Commands

1) df [options] [resource] 

report the summary of disk blocks and inodes free and in use

df is used to report the number of disk blocks and inodes used and free for each file system. The
output format and valid options are very specific to the OS and program version in use.
Syntax
df [options] [resource]
Common Options
-l local file systems only (SVR4)
-k report in kilobytes (SVR4)

2) du [options] [directory or file] report amount of disk space in use+
du reports the amount of disk space in use for the files or directories you specify.
Syntax
du [options] [directory or file]
Common Options
-a display disk usage for each file, not just subdirectories
-s display a summary total only
-k report in kilobytes (SVR4)
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3) hostname/uname display or set (super-user only) the name of the current machine
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4) kill [options] [-SIGNAL] [pid#] [%job] send a signal to the process with the process id number (pid#) or job
control number (%n). The default signal is to kill the process.
kill sends a signal to a process, usually to terminate it.
Syntax
kill [-signal] process-id
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5) man [options] command show the manual (man) page for a command
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6) passwd [options] set or change your password