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UNIX Training
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Welcome
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Who am I?
ABILASH KARUTHETHIL >> AB
Electronics and Comm. Engineering
Sun Certified System Administrator for Solaris OS Version 9
4 years Experience in IT and Solaris
Previously Worked for INFOSYS & EDS
Joined CTS on Sept2010
Associate Id : 253309 Here for sharing the UNIX Knowledge what I learnt from my
experience.
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May I Know you?
Name
Experience
Project
Knowledge about UNIX
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Course Map – Day 1
What is OS
UNIX History and Overview
Advantages of UNIX OS
File System Concepts
How to connect Unix Machine
File Manipulation commands
Directory Manipulation commands
More commands related to File system
Permission
User Account
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Course Map – Day 2
Shell
Controlling System Process
Scheduling the Jobs
Basic Networking
Useful commands
Important File Systems and Log Locations
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Day - 1
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UNIX History and Overview
UNIX was developed by AT & T researchers namely KenThompson and Dennies Ritchie for internal use. Later manyUnix flavor emerged named AIX from IBM, HP-UX from HP,Sun OS (Solaris) from Sun and so on.
Finnish college student LINUS TORVALDS developed Linux in1991. (Linus created Linux Kernal)
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Advantages of UNIX
Full multitasking with protected memory. Multiple users can run multipleprograms each at the same time without interfering with each other orcrashing the system.
Very efficient virtual memory, so many programs can run with a modest
amount of physical memory.
Access controls and security. All users must be authenticated by a validaccount and password to use the system at all. All files are owned byparticular accounts. The owner can decide whether others have read or
write access to his files.
A rich set of small commands and utilities that do specific tasks well -- notcluttered up with lots of special options.
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Advantages of UNIX
Ability to string commands and utilities together in unlimited ways toaccomplish more complicated tasks -- not limited to preconfiguredcombinations or menus, as in personal computer systems.
A powerfully unified file system. Everything is a file: data, programs, and allphysical devices. Entire file system appears as a single large tree of nesteddirectories, regardless of how many different physical devices (disks) areincluded.
Available on a wide variety of machines - the most truly portable operatingsystem.
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File system Concept
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File System, File & Directory
Unix is managed by File system.
File system - Hierarchical arrangement of files and directories
File – Collection of data items stored on the disk. It is may beraw data, Music file etc.
Directory – Contains the group of files.
In Unix everything is a file,(including H/W, Configuration data)
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File System, File & Directory
Files are grouped in the directory structure. The file-system is arrangedlike hierarchical tree (inverted)structure.
The top of the tree is called “root” which usually contains several sub-
directories. In UNIX “/”(forward slash) is used to present the “root”.
/root
lib bin
Name are case-sensitive, Delimited by the / (forward slash)
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File Components
File has three components
File Name – is a object must often used to access and manipulate the file
Inode - is a object of the Unix OS used to record the information about thefile
Data block - Unit of the dsik space that are used to store the data
Filename associated with inode and it give access to the data block
Filename --> Inode --> Datablock
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File Types
Regular File - All files are regular file. Ex : Text file, Binary file etc.
Directory - Contains any kind of files
Device file – It is provide the access to the device. There are two types indevice file. Block special file : communicate with h/w with block of data atime. Character file : Communicate with h/w one char a time.
Symbolic Link – It is point to another file. It contains the pathname of thefile to which it point. The size of the file is always matches the number ofthe characters in the path name it contains. It can be point any file,directory or other symbolic link.
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Home Directory
A Home directory is a file system directory on a multi-user operatingsystem containing files for a given user of the system.
Home directory will be created, when user created on the system
Separating user data from system-wide data avoids redundancy
A user will be automatically placed into their home directory upon login
The ~ (tilde character) shorthand command refers to that particular users
home directory
Example : /export/home/shandy – is the home directory of the usershandy.
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Pathnames
Absolute Pathnames
In the previous tree/users/usern/file1 isan absolute
pathname.
Relative pathnames
If you are already inthe users directory,the relative pathname
for file1 is usern/file1.
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How to Connect the Unix
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Connect the Unix Machine
We connect the Unix machine using putty exe, if machine is located inremote. It is open source software we can get it from internet.
If you run the putty.exe, It will ask the details like below
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Connect Unix Machine
Enter IP Address of the machine or name into the filed Host Name andselect respective protocol to connect the server. Normally we choose SSH.Then click open, It will ask the login name Like below window
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Connect Unix Machine
Once Login name entered, It will ask password for the user entered in thelogin prompt. Once you entered the password. It will logon the machine.
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File Manipulation Commands
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File Manipulation Commands
Create the file – cat & viEx :
$$ cat > hi
Red
Blue
<control-D>
List the the file – ls command
Ex :$$ ls –l hi
-rw-r--r-- 1 191278 staff 9 Oct 13 02:21 hi
$$
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File Manipulation Commands
View the file – cat, more, less, head, tailEx :
$$ cat hi
Red
Blue
$$
Copy the the file – cp command
Ex :$$ cp hi hello
$$
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File Manipulation Commands
Rename the file – mv commandEx :
$$ mv hi hello
$$
Delete the the file – rm command
Ex :
$$ rm hi
$$
Modify the file – vi command
Ex :
$$vi hi
$$ 26
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Vi Editor
Vi : the “Visual editor”, Standard Linux and Unix editor
To Create new file or opening the existing file
$vi {option} file name
If the file exists, the file is opened and content are displayed
If the file doesn’t exists, vi creates it when the edits are saved for the first time
Options : -m file is not modifiable, -x encrypt file when saving and decrypt filewhen editing, and so on.
Entering insert mode
a append mode, i insert before cursor
To exit insert mode, hit <Esc> key
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Vi Editor
Manipulation in vi editor
<esc> +yy – To copy the content of current cursor line
<esc> +3yy – To copy the content of 3 line below current cursor line
<esc> +p – To paste the single line
<esc> +dd – To delete the current cursor line <esc> +5dd – To delete five lines
<esc> +cc – To cut current cursor line
Saving and Exiting : ex mode
<esc> : wq – Save and quit the file
<esc> : wq! – Forcing to change and quit
<esc> : w! – Don’t exit, forcible save the file
<esc> :x – Save and exit the file
<esc> :q! – Forcible exit witout save the file28
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Directory Manipulation
Commands
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Directory Manipulation Commands
Create the Directory – mkdir command
Ex :
$$ mkdir test
$$
Change the Directory – cd command ( You can use both absolute andrelative path name for changing the directory)
Ex :$$ cd /export/home/shandy/test
$$
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Directory Manipulation Commands
Delete the Directory – rmdir (if only directory is empy) & rm -f commandEx :
$$ rmdir test
$$
$$ rm –f test
Rename the Directory – mv command ( You can use both absolute andrelative path name for changing the directory)
Ex :
$$ mv test test1$$
Present work Directory – pwd command
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More Commands
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More Commands
Command to check inode number for the file
$ ls -i hi
6219 hi
$
6219 – is a inode number
Command to create a symbolic link
$ ln -s hi hello
$ ls –ltr
-rw-r--r-- 1 w142922 staff 9 Oct 13 02:21 hi
lrwxrwxrwx 1 w142922 staff 2 Oct 14 04:06 hello -> hi
$
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More Commands
Command to check file system usage
$ df -k /
Filesystem kbytes used avail capacity Mounted on
rtpool/ROOT/s10s_u6wos_07b
30449664 10074647 11687398 47% /
$ du -h /export/home/191278
7K /export/home/191278
$
Command to find the file$find <dir> {condition} {action}
$ find /export/home/191278 -name hi
/export/home/191278/hi
$34
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More Commands
Archiving the files : - Placing Many file into one target file
Creating the tar
tar –cvf tar_file_name file
Ex :
$tar –cvf shans.tar hi hello
Inspecting the tar
$ tar –tvf shans.tar
Above command display list of all files in the archive
Extracting the archive
The archive will be extracted in the current directory
$tar –xvf shans.tar
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Permission
i i
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Permissions
There are three types of file access supported by UNIX.
r – read, view the contents of a file or a directory
w –write, edit file/directory contents
x –execute, run executable file
Here’s an example
Suppose you type in ls -l and the result is
- rwx r-x r-- 1 hans doc 858 Aug 22 22:28 hw1
What do all these symbols mean?
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Permissions
-rwx r-x r-- 1 hans doc 858 Aug 22 22:28 hw1
typeowner
groupsize Modification
date/time
File name
User
permissions
Group
permissions
Other
Permissions
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P i i
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Permissions
read=4;write= 2;execute=1rwx r-x r--
4 + 2 + 1
7 5 4
4 + 0 + 1 4 + 0 + 0
P i i
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Permission
rwx r-x r-- is a symbolic way to specify file modes, while 754 isa numeric way (remember 7 111, 5101, 4100 ? ). Howwould you represent this file mode numerically?
--x --x –wx
How would you represent this bit string symbolically?6 1 4
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P i i Ch i d
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Permission Changing command
chmod - command to change the access mode of a file
Ex :
Before :
-rw-r--r-- 1 191278 staff 0 Oct 15 02:42 script.sh
Run the command :
$chmod 755 script.sh or $chmod u=rwx,g=rx,o=rx script.sh
After :
-rwxr-xr-x 1 191278 staff 0 Oct 15 02:42 script.sh
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Sti k bit P i i
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Sticky bit Permission
The Sticky Bit is a special permission that protects the files within apublicly writable directory.
If the directory permissions have the Sticky Bit set, a file can be deletedonly by the owner of the file, the owner of the directory, or by the root user.
This prevents a user from deleting other users’ files from publicly writabledirectories.
Use the ls command to determine if a directory has the Sticky Bitpermission set.
$ ls -ld /tmp
drwxrwxrwt 6 root sys 719 May 31 03:30 /tmp
The Sticky Bit displays as the letter “t” in the execute field for other.
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U k
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Umask
The umask (UNIX shorthand for "user file-creation mode mask") is a four-digit octal number that UNIX uses to determine the file permission fornewly created files
Default umask is 022 and it is defined in /etc/profile file.
If umask value is 022, File will be created with permission of 666-022 =644
If umask value is 022, Directory will be created with permission of 777 – 022 = 755
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User Account
U r A t
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User Account
Whoever required Unix server access, they should have the user id or login
id.
Main Components of a User Account
User name – A unique name that a user enters to log in to a system.The
user name is also called the login name.
Password – A combination of up to 256 letters, numbers, or specialcharacters that a user enters with the login name to gain access to asystem.
UID number – A user account’s unique numerical identification within
the system.
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U A t
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User Account
Group identification (GID) number – A unique numerical identificationof the group to which the user belongs.
Comment – Information that identifies the user
User’s home directory – A directory into which the user is placed afterlogin. The directory is provided to the user to store and create
User’s login shell – The user’s work environment is set up by the
initialization files that are defined by the user’s login shell.
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S t Fil Th t St U A t I f ti
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System Files That Store User Account Information
/etc/passwd - Authorized system users have login account entries
/etc/shadow - contains the encrypted passwords.
/etc/group - Defines the default system group entries
Root User : has complete control over the system.
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Day-2
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Unix Shell
Sh ll
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Shell
The shell is a command programming language that provides an interfaceto the UNIX operating system
Unix has many shells, they are Bourne shell (sh) - This is the original Unix shell written by Steve Bourne of Bell Labs. It is
available on all UNIX systems. This shell does not have the interactive facilites provided by modernshells such as the C shell and Korn shell.
C shell (csh) - This shell was written at the University of California, Berkeley. It provides a C-likelanguage with which to write shell scripts - hence its name
TC shell (tcsh) - This shell is available in the public domain. It provides all the features of the C shelltogether with emacs style editing of the command line
Korn shell (ksh) - This shell was written by David Korn of Bell labs. It is now provided as thestandard shell on Unix systems. It provides all the features of the C and TC shells together with a shellprogramming language similar to that of the original Bourne shell. It is the most efficient shell.Consider using this as your standard interactive shell.
Bourne Again SHell (bash) - bash provides all the interactive features of the C shell (csh) and the
Korn shell (ksh). Its programming language is compatible with the Bourne shell (sh). If you use theBourne shell (sh) for shell programming consider using bash as your complete shell environment.
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Unix Kernel
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Unix Kernel
A Unix kernel— the core or key components of the operating system — consists of many kernel subsystems like process management, memorymanagement, file management, device management and networkmanagement.
The kernel provides these and other basic services: separation betweenuser and system space, system calls, scheduling, timer and clock handling,.
As an illustration of the way that the shell and the kernel work together,suppose a user types rm myfile (which has the effect of removing the file
myfile). The shell searches the file store for the file containing the programrm, and then requests the kernel, through system calls, to execute theprogram rm on myfile. When the process rm myfile has finished running,the shell then returns the UNIX prompt % to the user, indicating that it iswaiting for further commands.
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Controlling the System Process
What is the Process
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What is the Process
A process is any program that is running on the system.
All processes are assigned a unique process identification(PID) number, which is used by the kernel to track andmanage the process.
The PID numbers are used by the root and regular users toidentify and control their processes.
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Viewing System Processes
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Viewing System Processes
The prstat or ps command examines and displays information about activeprocesses on the system.
Ex :
# prstat
PID USERNAME SIZE RSS STATE PRI NICE TIME CPU PROCESS/NLWP
1641 root 4864K 4520K cpu0 59 0 0:00:00 0.5% prstat/1
1635 root 1504K 1168K sleep 59 0 0:00:00 0.3% ksh/1
9 root 6096K 4072K sleep 59 0 0:00:29 0.1% svc.configd/11566 root 82M 30M sleep 29 10 0:00:36 0.1% java/14
1633 root 2232K 1520K sleep 59 0 0:00:00 0.1% in.rlogind/1
531 root 8200K 2928K sleep 59 0 0:00:12 0.1% dtgreet/1
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The state of the process
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The state of the process
cpu – The process is running on the CPU.
sleep – The process is waiting for an event to complete.
run – The process is in the run queue.
zombie – The process terminated, and the parent is not
waiting.
stop – The process is stopped.
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Killing Frozen Processes
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Killing Frozen Processes
You use the kill command or the pkill command to send a signal to one ormore running processes. You would typically use these commands to killan unwanted process.
The format for the kill command is:
#kill -signal PID
The format for the pkill command is:
#pkill -signal Process
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Killing Frozen Processes
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Killing Frozen Processes
Before killing the process, we need to findout the PID for process, Usingfollowing command we can find the PID for process
#pgrep -l mail
241 sendmail
240 sendmail or
# ps -e | grep sendmail
241 ? 0:00 sendmail
240 ? 0:02 sendmailThen you can kill using processname or PID
# pkill sendmail
# kill 241 (Default signal 15 )
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Killing Frozen Processes
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Killing Frozen Processes
To terminate more than one process at the same time, use the following
syntax:
# kill -signal PID PID PID PID
# pkill signal process process
Signal Number --- Signal Name --- Event --- efault Action
1 --- SIGHUP --- Hangup --- Exit
2 --- SIGINT --- Interrupt --- Exit
9 ---SIGKILL --- Kill --- Exit
15 --- SIGTERM --- Terminate --- Exit
Some processes can be written to ignore Signal 15. Processes that do not respondto a Signal 15 can be terminated by force by using Signal 9 with the kill or pkillcommands. You use the following syntax:
# kill -9 PID or # pkill -9 process
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Scheduling the Jobs
Scheduling an Automatic One-Time Execution of a
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Command
Use the at command to automatically execute a job only once at a specified time.
The format for the at command is:
#at -m -q queuename time date
#at -r job#at –l
-m - Sends mail to the user after the job has finished
-r job - Removes a scheduled at job from the queue
-q queuename - Specifies a specific queuetime - Specifies a time for the command to execute
-l - Reports all jobs scheduled for the invoking user
date - Specifies an optional date for the command to execute, which is either a monthname followed by a day number or a day of the week
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Scheduling an Automatic One-Time Execution of a
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Command
Ex :
# at 9:00 pm
at> find /export/home -name core -exec file {} \; >> /var/tmp/corelog
at> <EOT>
commands will be executed using /sbin/sh
job 1098648000.a at Mon Oct 25 21:00:00 2004
To display information about the execution times of jobs, perform the command:
# at -l 1098648000.a
1098648000.a Mon Oct 25 21:00:00 2004
For example, to remove job 1098648000.a from the at queue, perform thecommand:
# at -r 1098648000.a
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Scheduling an Automatic Recurring Execution of a
d
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Command
You can use the cron facility to schedule regularly recurring commands.Users can submit a command to the cron facility by modifying their crontabfile.
All crontab files are maintained in the /var/spool/cron/crontabs directory
and are stored as the login name of the user that created the cron job.
The cron daemon is responsible for scheduling and running these jobs.
crontab File Format :
A crontab file consists of lines of six fields each. The fields are separated byspaces or tabs. The first five fields provide the date and time the commandis to be scheduled. The last field is the full path to the command.
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Scheduling an Automatic Recurring Execution of a
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Command
Ex :
10 3 * * 0 /usr/sbin/log/adm
10 - The minute field can hold values between 0 and 59.
3 - The hour field can hold values between 0 and 23.
* - The day-of-month field can hold values between 1 and 31.
* - The month field can hold values between 1 and 12, January toDecember.
0 - The day-of-week field can hold values between 0 and 6. Sunday is 0. /usr/sbin/log/adm - The command field contains the full path name to the
command to be run by the cron utility.
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Crontab Command
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Crontab Command
The crontab command enables the user to view, edit, or remove a crontabfile.
Viewing a crontab File
To view the contents of the root crontab file, run the crontab –l command as theroot user.
Editing a crontab File
To Edit the content of the crontab using crontab –e command. Before executingthis command you have to set the editor as vi.
Removing a crontab File The correct way to remove a crontab file is to invoke the command:
# crontab -r username
Typical users can remove only their own crontab file. The root user candeleteany user’s crontab file.
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Controlling Access to the crontab Command
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Controlling Access to the crontab Command
You can control access to the crontab command with two files in the/etc/cron.d directory—the cron.deny file and the cron.allow file.
These files permit only specified users to perform crontab tasks, such ascreating, editing, displaying, or removing their own crontab files.
/etc/cron.d/cron.deny - The Solaris OS provides a default cron.deny file.The file consists of a list of user names of the users who are not allowed touse cron.
/etc/cron.d/cron.allow - The /etc/cron.d/cron.allow file does not exist bydefault, so all users (except those listed in the cron.deny file) can accesstheir crontab file. By creating a cron.allow file, you can list only those userswho can access crontab commands.
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Basic Networking
ftp Commands
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ftp Commands
The FTP (File Transfer Protocol) utility program is commonly used forcopying files to and from other computers. These computers may be at thesame site or at different sites thousands of miles apart. FTP is a generalprotocol that works on UNIX systems as well as a variety of other (non-UNIX) systems.
To connect your local machine to the remote machine, type
ftp machinename ( Ip address or machine name)
It will ask user name and password for login. Once you gave those details.,
It will allow to access the to the system, should have access on the requiredmachine for ftp access.
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ftp Commands
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ftp Commands
? - to request help or information about the FTP commands
ascii - to set the mode of file transfer to ASCII
binary - to set the mode of file transfer to binary
bye - to exit the FTP environment (same as quit)
cd - to change directory on the remote machine
delete - to delete (remove) a file in the current remote directory
get - to copy one file from the remote machine to the local machine
lcd - to change directory on your local machine (same as UNIX cd)
mget - to copy multiple files from the remote machine to the local
machine; you are prompted for a y/n answer before transferring each file mput - to copy multiple files from the local machine to the remote
machine; you are prompted for a y/n answer before transferring each file.
put - to copy one file from the local machine to the remote machine
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Other Useful Commands
Other Commands
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C
grep - looks for the string in the files. Ex : grep ‘string’ filname
diff - Compare the files and shows where they differ. Ex : diff filename1
filename2
wc - tells you how many lines, words, and characters there are in a file. Ex :wc filename
pwd - tells you where you currently are.
w- tells you who's logged in, and what they're doing. Especially useful: the'idle' part. This allows you to see whether they're actually sitting theretyping away at their keyboards right at the moment.
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Other Commands
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C
who --- tells you who's logged on, and where they're coming from.
finger username - gives you lots of information about that user.
last -1 username - tells you when the user last logged on and off and from
where.
talk username - lets you have a (typed) conversation with another user.
write username - lets you exchange one-line messages with another user
passwd - lets you change your password
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Other Commands
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C
Date - shows the current date and time.
cal - shows a calendar of the current month.
man commandname - shows you the manual page for the command.
Hostname – shows server information.
sort – used to sort content the file. Ex: sort filename. It only display outputin the screen.
tail filename – display last part of the file.
head filename – display first part of the file. 74
Other Commands
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history - list previously issued commands.
uptime - show system load, how long system has been up.
bg - put suspended process into background.
fg - bring process into foreground.
jobs - list processes.
^z - suspend current process
clear - clear terminal screen
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Other Commands
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exit - terminate a shell
logout - sign off; end session
man - find manual information about commands.
psrinfo - displays information about processors.
bc - a simple calculator
su - username – used to switch the user
format – Display the hard disk available on the system.
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Special commands and characters
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Redirection
< Routes input to command from file
> Routes output from command to file
>> Appends output to existing file
| Routes output between commands
Wildcards used in filenames
* Matches any number of characters
? Matches one character
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Important File system and Log
locations
Important File Systems
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p y
/ - Root file system contains the OS images
/var – File system contains variable data, like log etc
/usr/bin & /usr/sbin – contains the commands and executable
/export/home – Contains the user data
/opt – Contains the additional softwares
/swap – Virtual memory used for system process and programs
/usr/lib – Library files are stored
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Important Log Locations
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p g
/var/adm/messages – Contains all messages logged by OS.
/var/adm/lastlog - captures or record the last user and host info that login
to the server.
/var/adm/sulog - record of all attempts by users on the system to executethe su command.
/var/adm/loginlog - that logs unsuccessful attempts to access the system
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