The term “runlevel” which is frequently use in UNIX based operating system is refers to “Unix System V-style initialization” mode for operation.
There are seven runlevels , numbered from zero to six. “s” is used sometimes as a synonym for level 1. Operating system is boot by use only one runlevel, runlevels are not executing sequentially.
Runlevels are defining the state
whoami - print effective userid
Print the user name associated with the current effective user ID. Same as id -un.
display this help and exit
output version information and
who - show who is logged on
who [OPTION]... [ FILE | ARG1 ARG2 ]
Print information about users who are currently logged in.
same as -b -d --login -p -r -t -T -u
time of last system boot
print dead processes
print line of column headings
print system login processes
attempt to canonicalize hostnames via DNS
only hostname and user associated with
which - shows the full path of (shell) commands.
which [options] [--] programname [...]
Which takes one or more arguments. For each of its arguments it prints to stdout the full path of the executables that would have been executed when this argument had been entered at the shell prompt. It does this by searching for an executable or script
whereis - locate the binary, source, and manual page files for a command
whereis [-bmsu] [-BMS directory... -f] filename...
whereis locates source/binary and manuals sections for specified files. The supplied names are first stripped of leading pathname components and any (single) trailing extension of the form .ext, for example, .c. Prefixes of s. resulting from use of source code control
wc - print newline, word, and byte counts for each file
wc [OPTION]... [FILE]...
wc [OPTION]... --files0-from=F
Print newline, word, and byte counts for each FILE, and a total line if more than one FILE is specified. With no FILE, or when FILE is -, read standard input.
print the byte counts
print the character counts
print the newline counts
watch - execute a program periodically, showing output fullscreen
watch [-dhvt] [-n <seconds>] [--differences[=cumulative]] [--help] [--interval=<seconds>] [--no-title] [--version] <command>
watch runs command repeatedly, displaying its output (the first screenfull). This allows you to watch the program output change over time. By default, the program is run every 2 seconds; use -n or --interval to specify a different interval.
vmstat - Report virtual memory statistics
vmstat [-a] [-n] [-t] [-S unit] [delay [ count]]
vmstat [-s] [-n] [-S unit]
vmstat [-m] [-n] [delay [ count]]
vmstat [-d] [-n] [delay [ count]]
vmstat [-p disk partition] [-n] [delay [ count]]
vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity.
The first report produced gives averages since the last reboot. Additional
vdir - list directory contents
vdir [OPTION]... [FILE]...
List information about the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor --sort.
Mandatory arguments to long options are mandatory for short options too.
do not ignore entries starting with .
do not list implied . and ..
with -l, print the author of each file
print octal escapes
uudecode - decode a binary file
uudecode [-o outfile][file]
The uudecode utility shall read a file, or standard input if no file is specified, that includes data created by the uuencode utility. The uudecode utility shall scan the input file, searching for data compatible with one of the formats specified in uuencode, and attempt to create or overwrite the file