5. Redhat Linux : RHCE 6

5. Redhat Linux : RHCE 6

 

Networking
      
Clases in Network
-----------------
* Class A : 1-126  netmask:255.0.0.0
* Class B : 128-191 netmask:255.255.0.0
* Class C : 192-223 netmask:255.255.255.0
* Class D : 224-239 netmask:no netmask
* Class E : 240-254 netmask:no netmask
* loopback address : 127.0.0.0
* broadcast address : 255.255.255.255

Hostname
--------
* change permenanlty in /etc/sysconfig/network
* /etc/sysconfig/network-scripts/ifcfg-eth0 stores ifconfig details of eth0
* /etc/sysconfig/network-scripts/ifcfg-eth1 stores ifconfig details of eth1
* /etc/resolve.conf stores DNS details 
* /etc/services stores port infos
* /etc/rc5 stores apps to be started at shell startup and ending

      Network Services
      ----------------
NFS (Network File Sharing Service)
----------------------------------
* used for UNIX to UNIX file sharing(NFS V3)
* port used by NFS is 2049
* package for NFS is nfs-utils
* daemon(process that runs continoeusly in the background) is nfs
* /etc/exports stores the files to be shared
 /store(directory to share) domain.com(rw,sync)
 /store(directory to share) desktop1.domain.com(rw,sync)
 /store(directory to share) ip (rw,sync)
 /store(directory to share) 192.168.0.1/24(rw,sync)
 /store(directory to share) 192.168.0.1-12(rw,sync)
* well-known ports : connection oriented(tcp)
* short service ports : udp
* ping command sends ICMP packets
 Steps to do:
 -----------
 1. Go to server and edit /etc/exports file:
  /directory_to_share client_ip(rw,sync)
  service nfs restart
 2. Go to client and see 'showmount -e server_ip'
  create a directory and mount it
  mount -t nfs server_ip:/directory_shared /new_directory@client

Auto File System:
----------------
* used for Unix to unix file sharing
* files need to be shared should be placed any where
* give the location in /etc/auto.misc
* enable the changes update in /etc/auto.master

CIFS (Samba)
------------
* used for UNIX to Windows file sharing and NFS V4

vsftpd:
------
* used for UNIX to UNIX file sharing
* Very secure file transfer protocol
* port 21
* config file /etc/vsftpd/vsftpd.conf
* place sharing files in /var/ftp/pub

httpd:
-----
* used for UNIX to UNIX file sharing
* port 443 for https

ssh:
---
* Secure shell uses port 22 and RSA algorithm for encryption
* open-ssh package
* to get documents sshd
* /etc/ssh/ssh_config is the config file:
 DenyUsers user1,user2
 AllowUsers user1,user2
* scp(secure copy)
 scp source destination
 scp /root/file root@192.168.x.x:/file
 scp root@192.168.x.x:/file  /root/file 
* ssh without password:
 ssh-keygen at client side produce public keys and private keys at /.ssh
 copy public key to server using 'ssh-copy-id -i ~/.ssh/id_rsa.pub root@192.168.x.x'
 /etc/ssh/sshd_config edit for permitrootlogin=yes and login without password enabled

telnet:
------


/*
Commands for the day:
--------------------
* ethtool eth0      : checks the physical connectivity of network
* ifconfig etho ipaddress    : set static ip 
* ifup eth0      : eth0 enable
* ifdown eth0      : eth0 disable 
* ping ipaddress     : ping status
* ping 0       : loopback ping
* chkconfig nfs      : used for enabling at start level
* chkconfig nfs on     : used for enabling at start level in the present run level
* chkconfig --level 34 nfs off    : used for disabling at levels 3 and 4
* chkconfig --level 34 nfs on    : used for enabling at levels 3 and 4
* chkconfig --list nfs     : used for listing all levels
* service nfs restart     : restart nfs
* showmount -e server_ip    : shows the nfs files shared by server
* mkdir directory
* mount -t nfs server_ip:/store directory  : to mount the nfs shared files in the client
* system-config-network     : GUI tool to configure networking(permenant)
* service autofs reload     : restart autofs
* scp source destination    : secure copy
*