Redhat Enterprise Linux / CENTOS Support

Xen for CentOS7

Enable Repo :

#yum install centos-release-xen

#yum update

#yum install xen

verify kernel

#uname -r

#xl info

Setup Bridging :

ip route show | grep 'default' | awk '{print $5}'

nmcli con add type bridge con-name xenbr0 ifname xenbr0
nmcli con modify xenbr0 bridge.stp no
nmcli con modify xenbr0 bridge.hello-time 0

nmcli con show
nmcli con modify "System eth0" connection.master xenbr0 connection.slave-type bridge
systemctl restart network

RHEL8 - CENTOS8 Xen Dom0

Since KVM became default virtualization software from RHEL, after releasing of RHEL8 and CENTOS8 still XenSource RPMs are not available.

Fix for Zabbix4.0 installation on RHEL8 MariaDB10.3 error

There is problem on installing zabbix-server on RHEL8, while importing database schema error occurs.

Zabbix server version prior to 4.4 cannot work correctly with newer MariaDB versions out of the box.

Prior to MariaDB 10.2.26, 10.3.17, and 10.4.7, MariaDB didn't properly calculate the row sizes while executing DDL, so "unsafe" tables could be created, even with innodb_strict_mode=ON set. This was fixed by MDEV-19292.

shell> mysql -uroot -p<password>
mysql> set global innodb_strict_mode='OFF';

After importing Zabbix database schema

shell> mysql -uroot -p<password>
mysql> USE zabbix
mysql> alter table `host_inventory` modify `name` varchar(128) default '' not null, modify `alias` varchar(128) default '' not null, modify `os` varchar(128) default '' not null, modify `os_short` varchar(128) default '' not null;
mysql> set global innodb_strict_mode='ON';

MySQL Server is removed from Centos/RHEL 7 Repo

Big changes in open source world, i was just installing zabbix server and mysql database is required for zabbix. After installing Centos 7 from minimal install iso i didn't get mysql by "yum install mysql-server so i came to know about changes that "MySQL is no longer in CentOS’s repositories and MariaDB has become the default database" who knows mariaDB ??

any way you can still install mysql by installing official mysql community Yum's Repo file for "yum install mysql-server"

Method : Download and install from this url

http://repo.mysql.com/mysql-community-release-el7-5.noarch.rpm

or simply rpm -ivh http://repo.mysql.com/mysql-community-release-el7-5.noarch.rpm

Gnu Sed Utility

Example :

removing # (commented Lines) from a file

sed '/ *#/d; /^ *$/d' /sourcefile >/destfile

Cactiez Backup Restore

Restoring Cacti Backup from old server in easy steps .

Default Backup directory : /var/www/backups

tar -xzvf /var/www/backups/cacti-backup-year-month-Date.tar.gz

Data Base Import :

mysql cacti < /var/www/html/cacti-backup.sql
mysql syslog < /var/www/html/syslog.sql

Restart All CactiEz Services

Install centos6 from internet (netinstall)

Installing Centos6 / Rhel 6 From Network (Internet) :

We need ISO image from this links : image size is only 170 MB.

32 bit: http://linux.mirrors.es.net/centos/6.0/isos/i386/CentOS-6.0-i386-netinstall.iso
64 bit: http://linux.mirrors.es.net/centos/6.0/isos/x86_64/CentOS-6.0-x86_64-netinstall.iso

Burn Iso image to cd by your favorite image burner..

boot from cdrom and follow the instructions.

At Installation method menu select URL

configure ip address to access internet.

input this url for netinstall :

http://mirror.centos.org/centos/6/os/i386

Now install as normal installation.

how to make rouring in redhat 6

In RHEL6 / CENTOS6 /FEDORA you can add static roure by applying route add command. but it is a temporary route.

for static roure, you can do it by modifying route-eth files..

ath of file : /etc/sysconfig/network-scripts

modify route-eth0 or route-eth1 file on which Ethernet interface you want to add route,

if file is not present create a file

# vi /etc/sysconfig/network-scripts/route-eth0

add following lines :

ADDRESS0=X.X.X.X
NETMASK0=X.X.X.X
GATEWAY0=X.X.X.X

example :

ADDRESS0=192.168.10.0       Destination Network Address

NETMASK0=255.255.255.0      Destination Network Subnet mask

GATEWAY0=192.168.2.1        Gateway address for that network

IF YOU WANT MORE ROUTES TO BE ADDED, APPLY 1,2,3, ETC.

CentOS 6 Download Link

CentOS is a Fork / Clone of RHEL ( RedHat Enterprise Linux), Basically RHEL is a Linux Distribution Under GNU GPL License but not free. So CentOS is a project to provide Enterprise Linux Free of cost. There is no more technical difference between RHEL and CentOS. If you want to install RHEL, you must create account to download RHEL ISO file and it is evolution version so we highly recomend that you first try CentOS which is free and opensource..

These are the links for to download CENTOS 6 ISO File, Download it and Burn it on CD / DVD with your favourite Burning program.

CentOS 32 bit DVD ISO File

CentOS 32 bit Live CD ISO File

CentOS 32 bit Live DVD ISO File

CentOS 64 bit DVD -1 ISO File

CentOS 64 bit DVD -2 ISO File

CentOS 64 bit Live CD ISO File

CentOS 64 bit Live DVD ISO File

How-to-Configure Network in RHEL6 Centos6

In RHEL6 and CentOS6 there is not System-Config-Network Script available which was very handy and useful.. Its good thing that now your require Basic Knowledge of Linux config File.. which is a best practice for Real Unix / Linux Admins.

Basically /etc contains Config files for system.
for network there is a directory called /etc/sysconfig/network-script/

There are ifcfg-eth(number) file for every Ethernet interface e.g ifcfg-eth0 for Ethernet 0, ifcfg-eth1 for Ethernet 1

Now create a file or Edit a file called /etc/sysconfig/network-script/ifcfg-eth0

------------------------------------------------------------------------------------------------------------

DEVICE=eth0

IPADDR=192.168.0.1
NETMASK=255.255.255.0
NETWORK=192.168.0.0
BROADCAST=192.168.0.255
ONBOOT=yes
BOOTPROTO=none
USERCTL=no

------------------------------------------------------------------------------------------------------------

These are the values which you can configure in config file :

DEVICE=devicename, where devicename is the name of the physical network device.

IPADDR=ipaddr, where ipaddr is the IP address.

NETMASK=netmask, where netmask is the netmask IP value.

NETWORK=network, where network is the network IP address.

BROADCAST=broadcast, where broadcast is the broadcast IP address.

ONBOOT=answer, where answer is yes or no. Do the interface need to be active or inactive at boot time.

BOOTPROTO=proto, where proto is one of the following :

none - No boot-time protocol should be used.

bootp - The bootp now pump protocol should be used.

dhcp - The dhcp protocol should be used.

USERCTL=answer, where answer is one of the following:

yes - Non-root users are allowed to control this device.

no - Only the super-user root is allowed to control this device.

RHEL 6, CENTOS6