Transcript UNIX Operating System

ITEC400 Winter 2017 Week Six
Professor Robert D’Andrea
Agenda
Administrative Issues
Link of the Week
This Week’s Expected Outcomes
Review for midterm exam
Moving around in UNIX
Break-Out Problems
Upcoming Deadlines
Hands-on Information
Lab Assistance, Questions, and Answers
Administrative Announcements
The midterm exam will be administered the seventh
week of the term from February 20 through 25, 2017.
Exam:
True/False
60 questions (1 point)
Multiple Choice
40 questions (1 point)
Essay
5 questions (5 points)
Link of the week
http://www.thefreecountry.com/perlscripts/index.shtml
Free Perl and CGI scripts
Perl is dual licensed under both the Artistic
License and the GNU General Public Licenses.
Distributions are available for most operating
systems.
Link of the week
Why do we love Perl?
The Perl Programming Language currently has
21,000 Comprehensive Perl Archive (CPAN)
modules.
The CPAN has over 18,000 open source modules
available for download.
Perl is a highly capable, feature-rich
programming language with over 30 years of
development.
Parts of the Perl language are still actively being
pursued. Perl has over 300 local community groups.
Perl 6 is a sister language, part of the Perl family.
This Week’s Expected Outcomes
Upon successful completion of this module, the student
will be able to:
 Create makefile scripts for software programs.
 Interfaces
 Use pattern rules in make files.
 Create an effective PowerPoint presentation.
 Create make files with multiple targets.
 Install software packages on a server.
UNIX Operating System
SCSI interface
SCSI (pronounced SKUH-zee and sometimes
colloquially known as "scuzzy"), the Small Computer
System Interface, is a set of ANSI standard electronic
interfaces that allow personal computers to
communicate with peripheral hardware such as disk
drives, tape drives, CD-ROM drives, printers, and
scanners faster and more flexibly than previous
interfaces. Developed at Apple Computer and still used
in the Macintosh, the present set of SCSIs are parallel
interfaces. SCSI ports continue to be built into many
personal computers today and are supported by all
major operating systems.
UNIX Operating System
Linux device naming
This section provides information to help you
understand naming patterns for devices on Linux.
 Special device files are used by kernel drivers to control a
device. There can be more than one special device file
that maps to the same physical device. For example, in a
multipath environment with four paths to the same
device, four different device files will map to the same
physical device.
 The device files are located in the /dev directory and are
addressed by a major and minor number pair. Fiberchannel attached devices are managed as SCSI disk
devices by the sd driver. Thus, each of the attached
storage unit LUNs has a special device file in the Linux
directory /dev.
UNIX Operating System
SCSI disk devices have special device files that
start with an ‘sd’ prefix, and have the following naming
format:
/dev/sd[a-z][a-z][1-15]
Names without a trailing digit refer to the whole
disk, while names with a trailing digit refer to a
partition of that whole disk. By convention, SCSI disks
have a maximum of 16 minor numbers mapped to a
single disk. Thus, for each whole disk, there is a
maximum of 15 partitions per disk because one minor
number is used to describe the entire disk (for example
/dev/sda), and the other 15 minor numbers are used to
refer to partitions for that disk (for example /dev/sda1,
/dev/sda2, etc).
UNIX Operating System
ls -l /dev/sda*
brw-rw---brw-rw---brw-rw---brw-rw---brw-rw---brw-rw---brw-rw---brw-rw---brw-rw----
1 root disk
1 root disk
1 root disk
1 root disk
1 root disk
1 root disk
1 root disk
1 root disk
1 root disk
8,
8,
8,
8,
8,
8,
8,
8,
8,
0 May 24 08:09 /dev/sda
1 May 24 08:09 /dev/sda1
10 May 24 08:09 /dev/sda10
11 May 24 08:09 /dev/sda11
12 May 24 08:09 /dev/sda12
13 May 24 08:09 /dev/sda13
14 May 24 08:09 /dev/sda14
15 May 24 08:09 /dev/sda15
2 May 24 08:09 /dev/sda2
UNIX Operating System
ls -l /dev
brw-rw---- 1 root disk
8, 0 Jan 28 00:33 sda
brw-rw---- 1 root disk
8, 1 Jan 28 00:33 sda1
brw-rw---- 1 root disk
8, 2 Jan 28 00:33 sda2
======================================
crw-rw-rw- 1 root tty
5, 0 Feb 4 09:59 tty
crw--w---- 1 root tty
4, 0 Jan 28 00:33 tty0
crw------- 1 root root 4, 1 Jan 28 00:35 tty1
crw--w---- 1 root tty
4, 10 Jan 28 00:33 tty10
crw--w---- 1 root tty
4, 11 Jan 28 00:33 tty11
crw--w---- 1 root tty
4, 12 Jan 28 00:33 tty12
crw--w---- 1 root tty
4, 13 Jan 28 00:33 tty13
UNIX Operating System
Major and minor numbers
When accessing a device file, the major number
selects which device driver is being called to perform
the input/output operation.
The minor number is used by the kernel to
determine exactly which device is being referred to.
Depending on how your driver is written, you can
either get a direct pointer to your device from the
kernel, or you can use the minor number yourself as an
index into a local array of devices. Either way, the
kernel itself knows almost nothing about minor
numbers beyond the fact that they refer to devices
implemented by your driver.
UNIX Operating System
Major and minor numbers
$ ls -l /dev/hda
brw-rw---- 1 root disk 8, 0 mars 9 07:56 /dev/sda
Permissions
Owner
Group
Major device number
Minor device number
Date
Hour
Device name
UNIX Operating System
TTY and PTS
TTY originally meant, teletypewriter, but now it
means terminal on UNIX-like systems. It also means
any serial port on a UNIX/Linux system.
PTS means, pseudo terminal slave. The
difference between the tty and pts is the type of
connection to the computer. TTY ports are direct
connections to the computer like the keyboard/mouse
or a serial connection to the device. PTS connections
are SSH or telnet type connections. All of these
connections can be connected to a shell program which
will allow you to issue commands to the computer.
UNIX Operating System
TTY and PTS
drwxr-xr-x 2 root root
crw-rw-rw- 1 root tty
0 Jan 28 2014 pts
5, 0 Jan 22 10:14 tty
UNIX Operating System
Creating partitions
One big problem arises when splitting off lots of
separate partitions for new administrators, is settling on
the appropriate partition size. The appropriate partition
size of various partitions can vary considerably from
system to system. A workstation is likely to need a
small /var partition (100MB), but a mail or news server
may need a /var partition that is gigabytes is size.
Guessing the wrong size isn’t fatal, but is annoying. It
is time consuming to resize your partitions so that subdirectories on one partition can be stored on other
partitions.
UNIX Operating System
Partition recommendations for new Linux admins
Root (/) required, and swap is a good idea. Set root some
where between 5-25GB
/boot can be helpful on HDD with 8GB
As you gain more experience, you may break off other
directories into their own partitions on subsequent installations
or when upgrading disk hardware.
Keep the partitions simple!
Linux traditionally uses a tool for disk partitioning called
fdisk (fixed disk).The fdisk command name is followed by the
name of the disk device you want to partition, fdisk /dev/hda to
partition the primary master PATA disk.
UNIX Operating System
PATA
Parallel ATA is an Integrated Development
Environment (IDE) standard for connecting storage
devices like hard drives and optical devices to the
motherboard. PATA generally refers to the types of
cables and connections that follow this standard.
An IDE interface is an interface for mass storage
devices, in which the controller is integrated into the
disk or CD-ROM drive.
UNIX Operating System
UNIX Operating System
UNIX Operating System
Preparing a partition for use
After you have created a partition, you must
prepare it for use. Preparing it for use is called,
“making a file system” or “formatting a partition.” This
involves writing low level data structures to disk. Linux
can read and modify these data structures to access and
store files in the newly created partition.
UNIX Operating System
Preparing a partition for use
Low-level formatting is the process of marking
out cylinders and tracks for a blank hard disk, and then
dividing tracks into multiple sectors. This process is
often called the “real” formatting since it creates
physical format which defines where the data is saved.
If users perform low-level formatting when data have
been installed, all existing files will be erased, and it is
almost impossible to recover them. Therefore, some
users make such a format to avoid privacy leakage.
Nevertheless, performing low-level formatting will
bring great influence on hard disk, thus shortening hard
disk service time. Therefore, it is not suggested.
UNIX Operating System
Preparing a partition for use
High level formatting creates a file system. Hard
Disk Drive (HDD) are low-level formatted at the
factory and should not need to be low-level formatted.
UNIX Operating System
Preparing a partition for use
After a low-level formatting has been completed,
users need to make high-level formatting which makes
it possible to save data and should be done on a
partition. It is the process of writing a file system,
cluster size, partition label, and so on for a newly
created partition or volume. And we can also say highlevel formatting just clears data on hard disk, generates
boot information, initializes FAT, and labels logical bad
sectors when the partition has existed. This process
does no harm to hard disk in general situations, so we
suggest taking such a format to fix a logically damaged
partition or device, for example, Windows asks to
format a SD card.
UNIX Operating System
Common file system types
Linux supports both native file systems and those
intended for other operating systems.
Ext2fs (The Second Extended File System)
Good for small /boot partition (2TB)
Non-journaling
Reliable file system throughout 1990s.
Ext3fs (The Third Extended File System)
Journaling
Better reliability, extension of ext2fs.
Works well with very large disks (2TB)
UNIX Operating System
Journaling file system
A journaling file system keeps track of the changes that
will be made in a journal (usually a circular log in a dedicated
area of the file system) before committing them to the main file
system. In the event of a system crash or power failure, such file
systems are quicker to bring back online and less likely to
become corrupted.
Updating file systems to reflect changes to files and
directories usually requires many separate write operations. This
makes it possible for an interruption (like a power failure or
system crash) between writes to leave data structures in an
invalid intermediate state.
UNIX Operating System
Journaling file system
Depending on the actual implementation, a
journaling file system may only keep track of
stored metadata, resulting in improved performance at
the expense of increased possibility for data corruption.
Alternatively, a journaling file system may track both
stored data and related metadata, while some
implementations allow selectable behavior in this
regard.
UNIX Operating System
Common file system types
Ext4fs (The Fourth Extended File System)
Works well with very large disks (over
16TB)
Journaling
Improved performance
ReiserFS
Journaling
Better reliability
Works well handling large numbers of
small files.
UNIX Operating System
Installation Software Package Methods
Package manager
- What are the tasks of a package manager?
- The version of UNIX dictates which
package manager will be used.
- Many Linux versions utilize the Debian
Package Manager.
Manual
- The utilization of makefiles or shell
scripts to automate the install as much as
possible.
- On occasion, the installation of software
is done by sending the source code to the
site.
- What steps are required to install a new
software version?
- How is a “configure” script utilized?
UNIX Operating System
Installation Software Package Methods
Package manager
- Linux uses yum and rpm as there package
manager.
- Software has to be set or identified to use
rpm. Otherwise, the software is
configured manually.
UNIX Operating System
Test_build.sh script
The test_build.sh script is used to execute the make
command which in turn will call the makefile.
test_build.sh -> make -> makefile
UNIX Operating System
UNIX Operating System
Make command
The make utility is a software
engineering tool for managing and
maintaining computer programs. Make
provides most help when the program
consists of many component files. As the
number of files increase in a project, so to
does the compile time, and complexity of
compilation. The likelihood of an error
occurring with human(s) manageability is
high.
UNIX Operating System
Makefile
Make goes through the makefile (descriptor) file
first starting with the target it is going to create. Make
looks at each of the target’s dependencies to see if
they are listed as targets. It follows the chain of
dependencies until it reaches the end of the chain and
then begins backing out and executing the commands
found in each target's rule. Actually every file in the
chain may not need to be compiled. Make looks at the
time stamp for each file in the chain and compiles
from the point that is required to bring every file in
the chain up to date. If any file is missing it is
updated if possible.
UNIX Operating System
Makefile components
Comments within a makefile (#)
makefile continuation lines (\)
The rule tells make both what and
how to make a file
Dependency Line is a line with a colon (:)
test_build.sh contains the make
command which calls the makefile.
The test_build.sh script is located in
the /tmp directory.
UNIX Operating System
Key Points about the makefile
1. Makefile recompiles all source files for
an entire project.
2. Makefile recompiles only those files
that have different time stamps.
3. Bottom up control flow.
4. Rules are shell commands.
UNIX Operating System
Key Points about the makefile
The file names used in this example have been
abbreviated for simplicity.
C++ compilations end in .cpp suffix.
The .c suffix extension causes the C compiler to be
invoked.
The .o suffix represents a object file.
The .h suffix represents a header file.
The g++ is a compiler, and not a preprocessor.
The g++ builds object code from your C++ program
source.
The –c option, compiles source to object code.
The –o option, compiles object code.
UNIX Operating System
Other software products that perform similar
bundling operations
- ANT developed by Apache Jakarta
- ANT2 supplied from the Free Software
Foundation which is part of Red Hat.
What is a dependency between source files?
main.cpp  employee.cpp  address.cpp
What are the two parts of a dependency rule?
1) What files a file is dependent on?
2) Rule that tells how to recompile the file
What are the differences between a makefile and a shell
script?
The rules in a makefile are executed based on
dependency, and not sequential order. Scripts execute in
sequential order.
UNIX Operating System
UNIX Operating System
Hash initialization
my %colors = (“black”, 0xff0000,
“orange”, 0x00ff00, “blue”, 0x0000ff);
my %colors;
$colors{black] = 0xff0000;
$colors{orange} = 0x00ff00;
$colors{blue} = 0x0000ff;
For better reading and understanding use
the => operator.
UNIX Operating System
Hash initialization
Comma => arrow
The comma-arrow (=>) operator is
used to initialize the % hash member
variable. The left side of the comma-arrow
operator is expected to be a simple string
and therefore it is not necessary to be
quoted.
UNIX Operating System
Hash initialization
my %colors = (
black => 0xff0000,
orange => 0x00ff00,
blue => 0x0000ff,
);
UNIX Operating System
Perl Hash table is an unordered set of
scalars, accessed by some string value that is
associated with each scalar.
Keys are 12, 19, and 30.
Values are gray, black, and red.
%colormap=(
“12” => “gray”,
“19” => “black”,
“30” => “red”,);
%colormap = (“12”, “gray”, “19”, “black”, “30”,
“red”);
%members = (John => "father", Paul => "son",
Marie => "daughter");
UNIX Operating System
Keys & Values
%colormap = (“12”, “gray”, “19”, “black”, “30”, “red”);
@codes = keys %colormap; # codes array contains just
codes
@colors = values %colormap; # colors array contains the
colors
# Printing the values out of a hash table (hash_prt.pl)
while (($key, $value) = each(%colormap))
{
print $key, “, “, $value, “\n";
}
Executing the loop prints:
30, red
19, black
12, grey
UNIX Operating System
Hash Table
11
12
BLACK
13
RED
21
YELLOW
GRAY
22
23
BLUE
WHITE
31
32
33
GREEN
AMBER
GOLD
34
PINK
UNIX Operating System
UNIX Operating System
UNIX Operating System
Awk Script
# Author: Bob D'Andrea
# Script name: awksrc.sh
# Command line awk -f awksrc.sh test.txt
# Command line: awk -f awksrc.sh
/^$/ { print "This is a blank line." }
/[0-9]+/ { print "That is an integer." }
/[A-Za-z]+/ { print "This is a string." }
UNIX Operating System
Without options, print the desired
fields in any order.
awk ‘{ print $1, $2, $3, $4, $5 }’ names
The –F option changes the field
separator on the command line. The \t is an
Escape Sequence for a horizontal tab.
awk –F”\t” ‘{ print $1 }’ names
UNIX Operating System
names File Content
Bob Dee
Bo Happy
Jane Smith
Razi Jake
222-40-1234 03/19/1947
444-20-2222 01/01/1945
324-78-9990 04/23/1978
564-54-9879 05/26/2005
male
male
female
male
The file named “names” contains the above
information. There are tabs in two places in the above
data. One tab is after the name and after the birth date.
UNIX Operating System
Fork() and exec()
The fork syscal is a technique used to
“divide” the parent process into two identical
parts. After the parent executes the fork() syscal,
the created child process is an exact copy of the
parent except for the return value. The two
processes can continue to run in the same
binary, but most generally, the child process
switches to running another binary executable
by issuing the exec() syscal.
UNIX Operating System
Fork() and exec()
The new child of the parent process has a
new PID. The fork() function returns the child’s
PID to the parent, while it returns 0 to the child
process, in order to allow the two identical
processes to know one from the other.
UNIX Operating System
Fork() and exec()
The parent can continue to execute or wait
for the child process to complete. After the child
discovers that it is a child, and it replaces itself
completely with another program so that the
code and address space of the original program
are lost. The child calls exec(), all data in the
original program is lost , and is replaced with a
running copy of the new program.
UNIX Operating System
Fork() and exec()
If the parent process decides to wait for the
child process to die, then the parent will receive
the exit code of the program that the child
executed. To prevent a child from becoming a
zombie, the parent will call the wait() function
on its children either periodically or when
receiving the SIGCHLD signal, which indicates
a child process has terminated.
UNIX Operating System
PID (Process ID)
When a parent process creates a child
process, the child inherits specific attributes
from the parent. The child inherits the parent’s
terminal type, home directory, stdin, stdout, and
stderr.
UNIX Operating System
UNIX Operating System
Column
UID
PID
PPID
Description Output from ps –f command
User ID that this process belongs to (the
person running it).
Process ID.
Parent process ID (the ID of the process
that started it).
UNIX Operating System
Options which can be used with ps command
-a
-x
-u
-e
Shows information about all users
Shows information about processes without
terminals.
Shows additional information like -f option.
Display extended information.
UNIX Operating System
Signals
Signals are a form of process
communication. Because they can come from
another process, the kernel or the process itself,
they might be better thought of as events that
occur as a program runs. A crude example might
be the bell most of us remember from our early
days in school; when the bell rang, we reacted
by switching from playful children to
industrious students.
UNIX Operating System
Signals
The kill –l command will display the
signals available on your system. The kill –l
<signal name> displays the signal code.
HUP
INT
QUIT
KILL
TRAP
IOT
FPE
ALRM
TERM
CHLD
STOP
CONT
BUS
UNIX Operating System
Signals
For each signal there is a default action, almost
all of which terminate the process. For most signals, a
program may specify another action—this is called
catching or handling the signal—or may specify that no
action occurs, which is called ignoring the signal. The
signal SIGKILL cannot be caught or ignored; it always
terminates a process.
UNIX Operating System
kill Command
Used to send a signal to another process.
The kill command is used on Linux and
other UNIX-like operating systems to terminate
processes without having to log out or reboot
(i.e., restart) the computer.
Format: kill [signal or option] PID(s)
kill -l
kill –l TERM
kill –l KILL
UNIX Operating System
kill Command Signals
UNIX Operating System
Demonstrate
test_build.sh
pid_ppid.sh
Moving Around in UNIX
umask
umask –S
diff
make
fork() and exec()
tty
w
Break-out problems
touch command
What function does the makefile provide a project?
What are the two parts of a dependency rule?
What language is used for writing makefile rules?
What two methods are used for installing software
packages?
Hands-On-Information
Lab Assignment 5-1, Makefile Exercise,
due February 19, 2017. Lab Assignment 61, Programming Assignment 1, due
February 26, 2017.
After class assistance
Questions?
Comments?
Concerns?
After each Franklin Live session, I will remain on the
session to provide assistance unless otherwise
indicated.
Lab Assistance available by phone and/or
email