RedHat / CentOS Cluster, Which ports need to be open within iptables

cman (Cluster Manager) UDP Ports 5404, 5405

# iptables -I INPUT -m state --state NEW -m multiport -p udp -s 192.168.1.0/24 -d 192.168.1.0/24 --dports 5404,5405 -j ACCEPT

# iptables -I INPUT -m addrtype --dst-type MULTICAST -m state --state NEW -m multiport -p udp -s 192.168.1.0/24 --dports

 dlm (Distributed Lock Manager) TCP Port 21064

# iptables -I INPUT -m state --state NEW -p tcp -s 192.168.1.0/24 -d 192.168.1.0/24 --dport 21064 -j ACCEPT

 ricci (part of Conga remote agent) TCP Port 11111

# iptables -I INPUT -m state --state NEW -p tcp -s 192.168.1.0/24 -d 192.168.1.0/24 --dport 11111 -j ACCEPT

 modclusterd (part of Conga remote agent) TCP Port 16851

# iptables -I INPUT -m state --state NEW -p tcp -s 192.168.1.0/24 -d 192.168.1.0/24 --dport 16851 -j ACCEPT

 luci (Conga User Interface server) TCP Port 8084

# iptables -I INPUT -m state --state NEW -p tcp -s 192.168.1.0/24 -d 192.168.1.0/24 --dport 8084 -j ACCEPT

 igmp (Internet Group Management Protocol)

# iptables -I INPUT -p igmp -j ACCEPT

Linux LVM

1. create LVM partition:

fdisk /dev/[disk]

change partition type from LINUX to LVM

2. initialization LVM partition:

pvcreate /dev/[disk_partiton1] /dev/[disk_partition2]

check commands:

pvs
pvdisplay

3. create LVM group:

vgcreate [group_name] /dev/[disk_partition1] /dev/[disk_partition2]

check commands:

vgs
vgdisplay

4. create logical volumes which is attached to group:

lvcreate -L[size]M -n [vol_name] [group_name]

check commands:

lvs
lvdisplay

5. format volumes:

mkfs.ext3 [LV_name_from_lvdisplay]

---

EXTEND
change size volume:

lvextend -L +[size]M [LV_name_from_lvdisplay]

change size partition:

resize2fs [LV_name_from_lvdisplay]

REDUCE

fsck -f [LV_name_from_lvdisplay]

change size partition:

resize2fs [LV_name_from_lvdisplay] [size]G

change size volume:
lvreduce -L -[size]G [LV_name_from_lvdisplay]

Force User to Change Password at First Login Fedora /Centos /Suse /Ubuntu

To setup this there are various ways, but I believe one of the very simplest one is the one I am going to explain below.

For ex: You created a new user “fake”:

# useradd fake

Create password for the user

# passwd fake
Changing password for user foo.
New UNIX password:
BAD PASSWORD: it is WAY too short
Retype new UNIX password:

Then to force the user to change the password at the first login, simply set the password to expiry:

#chage -d 0 foo

This command will set the password to expiry and will force user to change their password at the next login.

Setting it default for all new Users:

A system admin is one which who can do the work but a efficient system admin is the one who do the work manually first time and then make computer to work for him next time for same task. Same thing is true over here. You want all the new users added to your system, to be forced to change their password at the first login, update this file

#vi /etc/default/useradd

 GROUP=100
HOME=/home
INACTIVE=-1
EXPIRE=0 #(need to add zero "0")
SHELL=/bin/bash
SKEL=/etc/skel
GROUPS=video
CREATE_MAIL_SPOOL=no
UMASK=022

This file contains the details, what all settings will be applied to the new users created into the system with useradd command.

Just set the value of EXPIRE=0 in this file, and after that, every time when a new user will be created, they will be forced to change the password at the next login.

password duration:
for new accounts default settings are in /etc/login.defs
settings for current accounts are in /etc/shadow but we edit by command chage
chage -l [user] #check settings for user
chage -E "YYYY-MM-DD" [user] #set date when account expire, -1 means never
chage -M [nr] [user] #set maximum number of days between password change from last password change, -1 means never expire
chage -d "YYYY-MM-DD" [user] #set last password change
chage -W [nr] [user] #number of days of warning before password expires
chage -i [nr] [user] #set password inactive, when account is blocked after password expire

RedHat / CentOS 6 Bonding

Bonding

Bonding (also known as “Ethernet bonding”) is a computer networking arrangement in which two or more network interfaces on a host computer are combined for redundancy or increased throughput.
mode=0 (Balance-rr) – This mode provides load balancing and fault tolerance.
mode=1 (active-backup) – This mode provides fault tolerance.
mode=2 (balance-xor) – This mode provides load balancing and fault tolerance.
mode=3 (broadcast) – This mode provides fault tolerance.
mode=4 (802.3ad) – This mode provides load balancing and fault tolerance.
mode=5 (balance-tlb) – Prerequisite: Ethtool support in the base drivers for retrieving the speed of each slave.
mode=6 (Balance-alb) – Prerequisite: Ethtool support in the base drivers for retrieving the speed of each slave.

Note: Always append extra configuration in case of a rollback.

Configuring  Bonding

# cd /etc/sysconfig/network-scripts/

# vi ifcfg-bond0

1 2 3 4 5 6 7 8 9 10

DEVICE=bond0 USERCTL=no BOOTPROTO=none ONBOOT=yes IPADDR=10.0.0.10 NETMASK=255.255.0.0 NETWORK=10.0.0.0   TYPE=Unknown IPV6INIT=no

# vi ifcfg-eth0

1 2 3 4 5 6

DEVICE=eth0 BOOTPROTO=none ONBOOT=yes MASTER=bond0 SLAVE=yes USERCTL=no

# vi ifcfg-eth1

1 2 3 4 5 6

DEVICE=eth1 BOOTPROTO=none ONBOOT=yes MASTER=bond0 SLAVE=yes USERCTL=no

# vi ifcfg-eth2

1 2 3 4 5 6

DEVICE=eth2 BOOTPROTO=none ONBOOT=yes MASTER=bond0 SLAVE=yes USERCTL=no

Due to the fact that /etc/modprobe.conf has been deprecated in RedHat / CentOS 6, the process of bonding network interfaces has changed a bit.
Now instead of defining your bond in your /etc/modprobe.conf, you define it in /etc/modprobe.d/bonding.conf

# vi /etc/modprobe.d/bonding.conf

We’ll be using mode=6 (Balance-alb)
Append the following onto the end out your modprobe config file

1 2	alias bond0 bonding options bond0 mode=6 miimon=100

# servive network restart