Basic Unix commands

Basic Unix commands

 
 

• Login

• Change password ( Passwd )

• Check the date and time (date)

• Check the present working directory (pwd)

• Check the teminal ( tty& stty)

• Check the system uptime ( uptime)

• Check the user details (finger)

• Change the user details (chfn)

• Get details of current loggedinusers(who)

• Get the identification details ( id )

• Check name,flavour of os ( uname )

• Check the calendar ( Cal )

• Banner ( banner )

• host name ( hostname )

• clear ( To clear screen )

 

passwd


passwd command is used to

update/change user’s authentication

token(s).

 

Root user can change/reset the

password for other users .

 

 

In production environment generally

password expires in 90 days or after 1

year.

 

date

date command is used to print or set the system date

and time

 

Syntax: date +”<options>”

 

 

Some useful options :

 

%blocales abbreviated month name

(Jan..Dec)

 

%d day of month (01..31)

 

%D date (mm/dd/yy)

 

 

%F same as %Y-%m-%d

 

 

%H hour (00..23)

 

%I hour (01..12)

 

 

%m month (01..12)

 

 

%M minute (00..59)

 

%S second (00..60)

 

%T time, 24-hour (hh:mm:ss)

 

%y last two digits of year

 

%Y year (1970...)

 

Date - Example

 

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pwd,tty,stty,uptime,finger



pwd command is used to print name of current/working

directory

 

tty command is used to print the file name of the

terminal connected to standard input


stty command is used to change and print terminal line

settings


stty –a command is usedto print all current settings in

human-readable form


uptime - Tell how long the system has been running.


finger command is used tocheck the user information

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Example : pwd,tty,stty,uptime,finger

chfn,who

chfn - change your finger information

who - show who is logged on
Some useful options of who command :

-b  time of last system boot

-i add idle time as HOURS:MINUTES

-r print current runlevel

-u list users logged in

 

Run levels

 

•The runlevels used by RHS are:

•0 - halt (Do NOT set initdefault to this)

•1 - Single user mode

•2 - Multiuser, without NFS (The same as 3, if you do not have networking)

•3 - Full multiuser mode

•4 - unused

•5 - X11

•6 - reboot (Do NOT set initdefault to this)

Example : chfn,who,whoami,w
 

whoami - print effective userid

w - Show who is logged on and what they are doing.

id - print real and effective UIDs and GIDs

Some useful options of id command :

-g print only the effective group ID

-G print all group IDs

-n print a name instead of a number

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uname,cal,clear

uname - print system information
 
Some useful options of uname comand :

-a print all information

-n print the network node hostname

-r print the kernel release

-v print the kernel version

-m print the machine hardware name

-p print the processor type

cal - displays a calendar

Cal displays a simple calendar.  If arguments are not specified, the current month is displayed.The options are as follows:

 -1      Display single month output.  (This is the default.)

 -3      Display prev/current/next month output.

 -s       Display Sunday as the first day of the week.  (This is the default.)

-m      Display Monday as the first day of the week.

clear - clear the terminal screen

hostname, domainname , dnsdomainname , nisdomainname , ypdomainname

hostname - show or set the system’s host name

 

Some useful options of hostname command :
-s   short host name
-a   alias names
-i    addresses for the hostname
-f    long host name (FQDN)
-d   DNS domain name
-y   NIS/YP domainname

domainname - show or set the system’s NIS/YP domain name

dnsdomainname - show the system’s DNS domain name

nisdomainname - show or set system’s NIS/YP domain name

ypdomainname - show or set the system’s NIS/YP domain name

Answer yourself,the following

Questions ???

1)How to get the OS name ?

2)How to know since when the server is up ?

3)How to get the last boot time of server ?

4)How to get the details of user ?

5)How to know who all are currently logged in and

which program they are executing currently ?

6)How to get the current date and time ?

7)How to get yesterday’s date ?

8)How to get tomorrow’s date ?

9)How to print the date in the following format ?

      Todays date is : YYYY-mm-dd:HH-MM-SS

10) How to change the users information ?

11) How to get the id of a particular user ?

12) How to know the present working directory ?

13) How to know which terminal is associated with

your current session ?

14) How to get the current terminal settting details ?

15) How to see the calendar of March 1999 ?

16) How to see the calendar for the year 1992 ?

17) How to get the hostname ?

18)How to get the FQDN (Fully Qualified Domain Name) ?