Linux Networking
CIS230.0325
Why Linux/Unix?
• Configurability
▫ Customizable System to satisfy unique needs.
• Scalability
▫ Able to serve an increasing number of users with
out down time.
• Stability
▫ Exceptional design to avoid crashes
Daemon & HTTPD
• Daemon
▫ Linux Program
▫ Runs in the background
▫ Starts up and shuts down
with the system
• Httpd
▫ D for daemon
▫ Runs in the background
▫ Answers server request from
clients
Inetd & TCP Wrappers
• Inetd
▫ Links ports to associated
server domain
▫ Runs appropriate programs
that are requested
• TCP Wrappers
▫ Grants or denies Server
Request
▫ Logs network use
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Date
Time
Service requested
Clients name
Address
File Sharing
• FTP (file transfer protocol)
• NFS (network file system)
• To access shared file:
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file must be listed in the NFS server host file.
User must know location
Mount file using mount command (line prompt)
Able to view mounted file like directory
Network File System
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NFS allows users to view/share files in Unix/Linux
Allows users to access their files from virtually any computer
Virtual file system
NFS Request are stateless
▫ Repeats client request during system crash
▫ During reboot, server would then answer request like the system
crash never occurred
• Knfsd – Kernel network file system daemon
▫ Runs in Kernel mode
▫ Uses NFS tools to improve response time for
clients
Server Message Block
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SMB is a client/server protocol
Application and presentation level protocol
Runs on transport and network protocols
In charge of
▫ File sharing
▫ Printing
▫ Logins
Samba/Share
• Samba is server for sharing, printing, and login
services
• Share allows users in a SMB to share resources
in network
• Two components of samba:
▫ Smbd: responsible for file and print services and
executes users verifications
▫ Nmbd: applies name resolution and browsing
SWAT
• Samba Web Administration Tool allows system
administrator:
▫ Change Samba configuration
▫ Select shares
▫ Set verification requirements like user name and
password
Postscript/Ghostscript
• Postscript:
-Is used to optimize printing graphics and text
-Provides convenient language for printing with out
reference to any device features like printer resolution
• Ghostscript converts postscript documents to raster
( composed of pixels and dot) image. Because inkjet printers are
not compatible with postscript
Postscript is the Linux/Unix page description language.
LPD/CUPS
LPD (line printer daemon)
• Linux Print Spooler
• Starts when computer boots
• Waits for print request from
clients
• Holds prints jobs until
printer is ready
• Prints the next file on the
list
CUPS (common Unix printing system)
• Allows computer to act as a
print server
• Accept print jobs from clients
• Process and sends to
appropriate printer
• Consist of spooler, scheduler
and filter system
• Converts print data to a format
that the printer understands
Internet Printing Protocol
• IPP manages print jobs and queues
• Runs on HTTP and allows bidirectional communication
between server and client
• Allows search for available printers in the network
• Verifies which client can access server host
• Stores logs and provides accounting capability
• Offers compatibility with older LPD-style clients
Apache
• Open source web server used by Linux/Unix
• Powers more then half the web sites around the world
(ex. hotmail, yahoo)
• Displays and serves HTML pages hosted on a server to a
client browser
KHTTPD
• Kernel mode Linux daemon that provides a web
service
• Able to run on Apache
• Kernel mode speeds up serving of static pages
• Errors are able to bring down an entire system
• User based process are more stable
Apache pre-forking
• Creates multiple child processes to handle HTTP request
• Parents process checks to see child process are working properly
and coordinates everything
• As more HTTP request are made, more child process are created to
process them
• When HTTP goes idle, the parent would kill child processes to free
up resource
• If child process were to crash, the parent and other child would not
be effected
• This process make apache very reliable
Apache - Modular Architecture
• Provides basic http functionality and other modules to
provide additional functionality
• Supports dynamic shared object that permit loading of
external modules at a run time
• Provides Application Programming Interface (APT)
• Apache is fully customizable to the administrator or
programer
• Portable run-time layer provides
▫ File input/output
▫ Network input/output
▫ Own memory management routines
Apache Filter
• Accepts input from the standard input device
• modifies data and sends the results to the
standard output device
• Used internally to process internal functions
• When receiving a request, it delegates the
request to a single content handler module that
sends the data back to the client
Clusters & Beowulf
Clusters
Beowulf Clusters
• Consist of multiple computers,
each with its own O.S
• Works with high speed
network
• Goals
• Tightly connected network
computers dedicated to the
solution of a single problem
• Links multiple inexpensive
computers to achieve the
performance of a super
computer
• Low priced
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High performance
High availability
Load balance
Scalability
Manageability
Single System Image
• A SSI is a comprised of multiple resources such as
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▫ Networks
▫ Distributed Databases
▫ Or Servers
To act as a single unified powerful resource
Linked to form peer-to-peer network
Does not share client-server relationship
Managed by the operating system’s kernel
Unlike Beowulf clusters
▫ Does not need to be modified to use MPI
▫ Regular programs can run without modification
▫ Doesn’t need to be cluster aware to have benefits
Cryptic line commands vs. User-friendly interface