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Linux Essenciais and System Administration

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Key Knowledge Areas

Connecting machines and resources

Networking Configuration and Services

Networking

Terms and Utilitiesnetwork layerstcp/udpethernetportstcp/ipaddressingipv4ipv6subnet classessubnet maskscidr

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Main approaches to configuring a machine for network

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Configuring a machine for network access:

Static configurationDynamic configuration

Static configuration uses set parameters for configuration, which is known by machine and network and never changes. - Generally used with servers.

Dynamic configuration configures network machines on fly where a service on network provides all configuration parameters to a machine when it joins the network.- Generally used with workstations.

Network Configuration

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Dynamic configuration

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Dynamic configuration is the easiest to use.

The machine just needs to set up it’s interfaces with the DHCP protocol.DHCP: Dynamic Host Configuration Protocol.

•A lease is obtained from the DHCP server, providing all network configuration details for the client. •The lease expires after some amount of time and is renewed by the client to maintain network access.

Network Configuration

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Static configuration

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Static configuration requires four configuration parameters in order to allow full network functionality:

•IP Address•Netmask•Default Gateway or Router•DNS Server(s)

Network Configuration

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Static configuration

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Network Configuration

First two components of static configuration are IP address and netmask.These provide LAN-level accessifconfig Network Interface configuration toolEx: ifconfig eth0 192.168.0.100 netmask 255.255.255.0

Third configuration parameter is the default gateway.Provides access to inter-networking, or moving from just the local LAN to other LAN’sroute Kernel routing table tool - Displays and manipulates network routing tableEx: route add default gw 192.168.0.1

Fourth configuration info is List of IP addresses which provide the DNS service. Allowing name to IP address mapping To configure add name-server lines to /etc/resolv.confEx: nameserver 192.168.7.15- Also consider /etc/nsswitch.conf

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Static configuration

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Network Configuration

ifconfig and route directly manipulate the running kernel, and are not permanent changes to the system. After a reboot, changes will be lost.

To make IP address, netmask and gateway changes permanent edit two config files:

•/etc/sysconfig/network-services/ifcfg-eth0•/etc/sysconfig/network

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Services

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Network Services

Services: hundreds, thousands of different network services. each individual service might have one or a dozen apps which can provide the service.Ex: HTTP, SMTP, SSH, FTP, MySQL

HTTP Hypertext Transfer Protocol: Used to ship webpages and associated files across network. Servers: Apache, IIS, lighttpd

SMTP Simple Mail Transfer Protocol: Delivers email messages. Popular Servers: qmail, sendmail, postfix, exchange

SSH Secure Shell: Encrypted remote shell access. Server: OpenSSH

FTP File Transfer Protocol: Used to move files around the network. Popular Servers: wu-ftpd, vsftpd

MySQL: Powerful open-source relational database management systemMySQL is the server and the only one - service is defined and implemented by the application

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Fim de sessão

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