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redhat04

Configure Routing on RHEL

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Configure Routing Tables on RHEL

Edit the IP Table (one that will be applied permenantly even after reboot)

/etc/sysconfig/network-scripts/route- <interface name>

 

Apply the edited configuration file

/etc/sysconfig/network-scripts/ifup-routes <interface name>

 

Add dynamically (will be erased after reboot)

route add “______”

 

 

 

 

Configure DNAT on Routing Tables on RHEL

Configure with  specific ports

iptables -t nat -A PREROUTING -d 105.90.15.131 -p tcp –dport 22 -j DNAT –to-destination 172.26.1.131:22

 

Configured without port

iptables -t nat -A PREROUTING -d 105.90.15.131 -j DNAT –to-destination 172.26.1.131

iptables -t nat -A PREROUTING -d 105.90.15.130 -j DNAT –to-destination 172.26.1.130

 

Deleting the DNAT with port

iptables -t nat -D PREROUTING -d 105.90.15.131 -p tcp –dport 22 -j DNAT –to-destination 172.26.1.131:22

 

Deleting the DNAT without port

iptables -t nat -nL OUTPUT –line-numbers

iptables -t nat -D OUTPUT {number-here}

 

redhat03

Network Configuration on RHEL

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Network Configuration on RHEL

 

Check which switch is connected with your adapter

tcpdump -nn -v -i bond0 -s 1500 -c 1 ‘ether[20:2]==0x2000’

 

*change bond0 with your interface name

 

Check bond which interface is on active mode

cat /sys/class/net/bond0/bonding/active_slave

 

Check the current status of bonding interfaces

check /proc/net/bonding/bond#

 

Check switch adapter status

systool -c fc_host -v |grep port_state

 

 

 

 

Network Manager CLI

To see current status

ip addr

nmcli connection show

nmcli device status

nmcli general status (current status to the connectivity)

nmcli general logging (current logging status)

nmcli device show

nmcli device show “device_name” (for one specific device)

 

Create new network profile

nmcli connection add type ethernet con-name “name_of_profile” ifname “interface_name_to_be_used”

 

Modify new network profile

nmcli connection modify “interface_name” ipv4.addresses “ip_addr/subnet” ipv4.gateway “gateway_ip_addr” ipv4.dns “dns_ip_addr” +ipv4.dns “dns_ip_addr” connection.autoconnect yes ipv4.method manual

 

this will create new interface_name with ip address with subnet, and gateway with 2 dns ip address, autoconnect on boot with static method

 

Bring network interface up

nmcli connection up “interface_name”

 

redhat02

Firewalls on RHEL

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Here’s firewall configuration RHEL 6 and below

 

Check the status for reboot persistance

chkconfig –list | grep iptables

 

Command to add the firewall to accept traffic with port 22 on source 192.1.1.2

iptables -I INPUT 2 -p tcp –dport 22 -s 192.1.1.2 -j ACCEPT

 

Default location of iptables files 

/etc/sysconfig/iptables

 

Location of iptables configuration file

/etc/sysconfig/iptables-config

 

Stop & Start the iptables service

service iptables stop

service iptables start 

 

List all the iptables

service iptables status 

OR

iptables -L

 

Add iptables rule

iptables -A INPUT -p tcp -s 0.0.0.0./0 -m tcp –dport 20301 -j ACCEPT

 

Drop iptables rule

iptables -D INPUT -p tcp -s 0.0.0.0/0 -m tcp –dport 20301 -j DROP

 

Save the currently running iptables to the file and system

service iptables save (It automatically overwrites it to the /etc/sysconfig/iptables)

 

If you edited the iptable file and want to save it use

iptables-restore < /etc/sysconfig/iptables

 

If you edited the iptables via commands and want to save it

service iptables save

 
 
 
Here’s firewall configuration RHEL 7 and above
 
Check status & enable/disable firewall daemon
systemctl status firewalld
systemctl enable firewalld
systemctl disable firewalld
 
Get current firewall rules
firewall-cmd –get-default-zone
input the result zone as below
firewall-cmd –set-default-zone=home
firewall-cmd –get-active-zones
 
Check firewall daemon version
firewall-cmd –version
 
List all interfaces under specific zone
firewall-cmd –zone=public –list-interfaces
 
Add/Remove interfaces under specific zone
firewall-cmd –add-interface=eth0 –zone=public
firewall-cmd –remove-interface=eth0 –zone=public
 
Other helpful commands
firewall-cmd –get-services
firewall-cmd –permanent –get-services
firewall-cmd –panic-on (disable incoming and outgoing packets
firewall-cmd –help
 
Install & Open firewall daemon on GUI
yum install firewall-config firewalld-filesystem python3-firewall -y
firewall-config
redhat01

Check and maintain clustering on RHEL

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Check & Maintain clustering on RHEL

 

CLUSTER COMMANDS

 

Check Cluster Status

Check cluster status                                         clustat 

Check cluster status every x seconds         clustat -i [interval] 

Check cluster status with extra detail         clustat -l 

Check configured nodes and their votes    ccs_tool lsnode 

Display cluster nodes                                       cman_tool 

 

Cluster Resource Group Administration

Restart Resource in place                            clusvcadm -R [resource name] 

Relocate Resource to another member    clusvcadm -r [resource name] -m [member name] 

Disable Resource                                            clusvcadm -d [resource name] 

Enable Resource                                             clusvcadm -e [resource name] 

Freeze Resource                                             clusvcadm -Z [resource name] 

Unfreeze Resource                                         clusvcadm -U [resource name] 

 

Testing Cluster Services

Status resource in test mode                      rg_test test [cluster config] status service [resource-name] 

Start resource in test mode                         rg_test test [cluster config] start service [resource-name] 

Stop resource in test mode                          rg_test test [cluster config] stop service [resource-name] 

 

Cluster Software

cman                    – Red Hat Cluster Manager

lvm2-cluster       – Cluster extensions for userland logical volume management tools

rgmanager          – Open Source HA Resource Group Failover for Red Hat Cluster

ricci                       – Remote Cluster and Storage Management System 

 

Cluster Services

Cluster Manager  (cman) Manages the following services qdiskd, fenced, dlm_controld and gfs_controld

Cluster Logical Volume Manager  (clvmd)                 

Cluster Resource Manager  (rgmanager)  

Cluster Management & Configuration Daemon  (ricci)

 

Cluster Configuration Files

Cluster configuration file                               /etc/cluster/cluster.conf 

Cluster resource scripts                                 /usr/share/cluster/ 

 

Cluster Log File Locations

Resource Manager Log                                               /var/log/cluster/rgmanager.log 

Fencing Log                                                                    /var/log/cluster/fenced.log 

Quorum Disk Log                                                           /var/log/cluster/qdiskd.log 

GFS Log                                                                            /var/log/cluster/gfs_controld.log 

DLM Log                                                                          /var/log/cluster/dlm_controld.log 

Corosysnc Log                                                                /var/log/cluster/corosync.log 

 

Start ricci on both nodes and join cluster from GUI

[Stop Cluster]                                                  [Start Cluster]                    

# service luci stop                                           # service cman start

# service ricci stop                                          # service rgmanager start

# service rgmanager stop                             # service ricci start

# service cman stop                                       # service luci start

 

 

 

 

How to perform maintenance such as offline PM and Cluster failover/failback test

Procedures:

 

clustat

/etc/cluster/cluster.conf 

 

stop applications and database

 

stops process on both hosts:

clusvcadm -d mainservicegroup

service rgmanager stop                 

service cman stop

service corosync stop                                    

 

disable cluster from starting on reboot

chkconfig/systemctl rgmanager off/disable

chkconfig/systemctl cman off/disable

chkconfig/systemctl corosync off/disable

 

no database should be loaded & work on the maintenance!

clustat

df -h

yum -y update

reboot

 

start process on both hosts:

service cman start

service rgmanager start

 

enable cluster to restart upon reboot

chkconfig/systemctl rgmanager on/enable

chkconfig/systemctl cman on/enable

chkconfig/systemctl corosync on/enable

clusvcadm -e mainservicegroup   <— Enable on prod first

 

 

 

 

Failover & Failback test

Relocate Resource to another member (for Physical Server)

clusvcadm -r [resource name] -m [member name]

 

Migrate Resource to another member (for Virtual Server)

clusvcadm -M [resource name] -m [member name]

 

from primaryNode:

Enable Resource 

               clusvcadm -r mainservicegroup -m secondaryNode

 

from secondaryNode:

Enable Resource 

               clusvcadm -r mainservicegroup -m primaryNode

 

 
redhat00

Tips & Tricks on RedHat Enterprise Linux (RHEL)

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Here’s a few tips & tricks on RedHat Enterprise Linux (RHEL)

 

add/remove SNMP settings

edit the “/etc/snmp/snmpd.conf”

service snmpd reload

edit the “/etc/hosts.allow” as needed

 

List process & find what process is doing

ps aux

strace

 

Display cluster configuration

rpm -qa | grep -i cluster

clustat

pcs status

 

Get system information

on DellPowerEdge:

   racadm getsysinfo

   racadm lclog view

 

on RHEL hardware detects:

   dmesg

 

Reset login attempts for users

pam_tally2 -r (reset) -u (user) userName

 

Reset password expiration date

chage -I -1 -m 0 -M 99999 -E -1 userName