RedHat Linux Certification mode preparation

Reduntancy Array of Independent Devices

RAID-Reduntancy Array of Independent Devices:

-- to backup the data in secondary storage devices. -- it have a Software RAID: .It allows to combine several disk into a larger RAID devices. .A RAID devices can be configured to provide additional speed and reliabiliy. it compared to using an individual drive.

Logical Volume

Logical Volume:

--> To Create LVM partitions are using [8e]
--> Physical Volume Creation
--> pvcreate devicename1 devicename2..
Example:
# pvcreate /dev/hda10 /dev/hda11
# pvcreate /dev/sda10 /dev/sda11 [sata hard drive]

--> Volume group creation
--> vgcreate volumegroupname devicename1 devicename2
--> logical volume creation
# lvcreate -L size -n lv1 vg

To Create a file system:

mke2fs -j /dev/vg/lv1

mount /dev/vg/lv1 /data

/etc/fstab
--- /dev/vg/lv1 /data auto default 1 2

To extend a Logical Volume:

lvextend -L +200m /dev/vg/lv1
mount -0 remount /dev/vg/lv1

To reduce Logical Volume:

lvreduce -L -100m /dev/vg/lv1
mount -o remount /dev/vg/lv1

To Check:

ext2online /dev/vg/lv1 [in el4]

or
resize -t /dev/vg/lv1 [in el5]

Cron Tab

Cron Tab:

-->to execute a command for particular time.
#crontab -u username -e
Example:
#crontab -u root -e

min hr day of month month day of week
01 20 22 08 08

Example:

tar -cvf /root/backup/home /home
service crond restart

crond -l
-->it will be displayed to what information available in crond file.

Shut down to the Machine at Everyday:
min hr day of month month day of week
01 20 * * *
/sbin/init 0
service crond restart
service crond on

Note:

Package Name: crontaps

User Quota

User Quota:

--> to set a limited storage file system.Its called user User systems.
vi /etc/fstab
to set hard disk or particular user --> Userquota, defaults

Group Quota:

--> to set a limited storage file system.Its called Group quota systems.
vi /etc/fstab
to set hard disk or particular user --> groupquota, defaults

Remote Installation

Remote Installation:

It means to get from the server data [linux system file system] to install
in client machine thru YUM Method
Procedure:
--> First a copy to all that linux cd to store in a server.
--> Share the folder to nfs thru vi /etc/fstab 192.168.1.1/16
--> In client system first bootable cdrom, give cd to install such as
linux askmethod
--to give client IP address and gateway
Manual TCP/IP Configuration:
-- IPV4 address 192.168.1.1/16
-- gateway 255.255.255.0
--Name Server
--> give path with server ip address
--> nfs setup
NFS server name 192.168.1.240[to give whether ip address or name.]
Directory of server. [path]
then click to ok button.

Example: # Vi /etc/yum.respoes.d/rhel
-- ftp://server1.example.com/pub/server
-- ftp://server1.example.com/pub/updates

# yum install dialog (it is a package name)

# yum install kernel *(it is a package name)

Remote System:
To logon the remote system. It is centralized the data in network. Its also called VPN.
VPN:
Virtual Private Network, Those who are system want to connected to server in a network.It
is possible to login any one system in online thru VPN.

Firewall

Firewall:

Definition:
Firewall means that to protect from the several processing into a server.
Here firewall as a IPTABLES.
IPTABLES-Firewall:
iptables -L --> list out the entries
iptables -L --> flash the entries
iptables -L --> adding the new role
service ip tables save
-p --> specify protocols
-s --> source ip address
-d --> designation ip address
--sport --> source port address
--dport --> designation port address
--j --> applying the policy

ACCEPT --> allow
REJECT --> deny
DROP --> Temporary stop.

Example:
#iptables -A INPUT -P ICMP -s 192.168.0.0/24 -d 192.168.0.1 --j drop
- do not to ping the server ip to any system in a network.

Note:
vi /etc/sysctl.conf
line no 7 and 13 --> to change 0 to 1. both of it.
Don't to forgot to change the configuration file.
once time when am i used that method, that time i forgot to configured.