How to Update CentOS IP and Hostname via Bash Script

I have created below mentioned bash script which will help you to update the IP Address and the hostname of the CentOS machines via this bash script.

#!/bin/bash

read -p "Enter the new IP address i.e: 10.50.4.243/20 : " ip_address

read -p "Enter the new gateway i.e:- 10.50.0.1 : " gateway

read -p "Enter the new hostname i.e: co7-50-4-243 : " hostname

# Get the interface name

interface=$(ip route | awk '/default/ { print $5 }')

# Get the ip address

ipa=$(hostname -I | awk '{ print $1 }')

# Update the IP address and gateway

echo "Updating IP address and gateway..."

nmcli con mod "$interface" ipv4.address "$ip_address"

nmcli con mod "$interface" ipv4.gateway "$gateway"

# Update the hostname

echo "Updating hostname..."

hostnamectl set-hostname "$hostname"

# Update the /etc/hosts file

echo "Updating /etc/hosts file..."

echo "$ipa $hostname" >> /etc/hosts

# Restart the network service

echo "Restarting network service..."

systemctl restart NetworkManager

echo "IP address, gateway, hostname, and /etc/hosts file updated successfully."

Configure bonding/teaming on Redhat Linux

Having a multiple network card will not give any redundancy.In redhat Linux you need to configure bonding to accomplish the network level redundancy.Once you have configured the bonding/teaming by using two NIC cards,kernel will automatically detect the failure of any NIC and work smartly according to that without any riot.Bonding can be used for load sharing as well between two physical links.

NIC Details:

[root@mylinz2 network-scripts]# ifconfig -a |grep eth
eth2      Link encap:Ethernet  HWaddr 00:0C:29:79:17:FA  
eth4      Link encap:Ethernet  HWaddr 00:0C:29:79:17:04  
eth3      Link encap:Ethernet  HWaddr 00:0C:29:79:17:F0 

[root@mylinz2 network-scripts]#

Goal:

Configure bonding between eth2 and eth4 with name of bond0.

Step 1:

Add the below line in /etc/modprobe.conf to load the bonding module in to kernel.

# alias bond0 bonding

In redhat 6.3 , you need to create new file called “bonding.conf” under /etc/modprobe.d/ with below mentioned line.

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

alias bond0 bonding

Step 2:

Now time to create a bonding interface configuration file in /etc/sysconfig/network-scripts/ directory like the below one.

[root@mylinz2 network-scripts]# pwd
/etc/sysconfig/network-scripts
[root@mylinz2 network-scripts]# cat ifcfg-bond0 
#This is congiguration file for bond0.Used NIC's eth2 & eth4
DEVICE=bond0
IPADDR=192.168.10.25
NETMASK=255.255.255.0
USRCTL=no
ONBOOT=yes
BOOTPRO=none
BONDING_OPTS="mode=0 miimon=100"

[root@mylinz2 network-scripts]#

Step:3

Create a configuration files under “/etc/sysconfig/network-scripts/” for network interfaces if not exists.If exists,have a contents like the below one.

[root@mylinz2 network-scripts]# cat ifcfg-eth2
DEVICE=eth2
HWADDR=00:0C:29:79:17:FA
BOOTPRO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes

USERCTL=no

[root@mylinz2 network-scripts]# cat ifcfg-eth4
DEVICE=eth4
HWADDR=00:0C:29:79:17:04
BOOTPRO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes

USERCTL=no

Note:Do not copy paste the content from above output.MAC and DEVICE name will differ for each system.

Step:4

Now restart the network service to load the configuration.

Note:Do not restart the network service without server maintenance window.

[root@mylinz2 ~]# service network restart

Shutting down interface eth2:  Device state: 3 (disconnected) [  OK  ]

Shutting down interface eth4:  Device state: 3 (disconnected) [  OK  ]

Shutting down loopback interface:                             [  OK  ]

Bringing up loopback interface:                               [  OK  ]

Bringing up interface bond0:  Active connection state: activated

Active connection path: /org/freedesktop/NetworkManager/ActiveConnection/15

[  OK  ]

Bringing up interface eth3:  Active connection state: activated

Active connection path: /org/freedesktop/NetworkManager/ActiveConnection/16

[  OK  ]

[root@mylinz2 ~]#

Step:5

Verify whether “bond0” has come up with IP or not .

[root@mylinz2 Desktop]# ifconfig -a

bond0     Link encap:Ethernet  HWaddr 00:0C:29:79:17:FA  

inet addr:192.168.10.25  Bcast:192.168.10.255  Mask:255.255.255.0

inet6 addr: fe80::20c:29ff:fe79:17fa/64 Scope:Link

UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1

RX packets:22 errors:0 dropped:0 overruns:0 frame:0

TX packets:27 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:0 

RX bytes:3843 (3.7 KiB)  TX bytes:4169 (4.0 KiB)

eth2      Link encap:Ethernet  HWaddr 00:0C:29:79:17:FA  

UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1

RX packets:11 errors:0 dropped:0 overruns:0 frame:0

TX packets:15 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000 

RX bytes:2031 (1.9 KiB)  TX bytes:2064 (2.0 KiB)

eth4      Link encap:Ethernet  HWaddr 00:0C:29:79:17:FA  

UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1

RX packets:11 errors:0 dropped:0 overruns:0 frame:0

TX packets:12 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000 

RX bytes:1812 (1.7 KiB)  TX bytes:2105 (2.0 KiB)

In the above output,you can see NIC eth2 and eth4 have flag “SLAVE” and interface “bond0” has flag MASTER.Another thing you note both, the NIC interface will show same MAC address.

Step:6

Performing the live test to ensure bonding is providing the fault tolerance.

First i am removing the LAN cable from eth4 and let see what happens.

[root@mylinz2 Desktop]# ifconfig -a

bond0     Link encap:Ethernet  HWaddr 00:0C:29:79:17:FA  

inet addr:192.168.10.25  Bcast:192.168.10.255  Mask:255.255.255.0

inet6 addr: fe80::20c:29ff:fe79:17fa/64 Scope:Link

UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1

RX packets:22 errors:0 dropped:0 overruns:0 frame:0

TX packets:27 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:0 

RX bytes:3843 (3.7 KiB)  TX bytes:4169 (4.0 KiB)

eth2      Link encap:Ethernet  HWaddr 00:0C:29:79:17:FA  

UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1

RX packets:11 errors:0 dropped:0 overruns:0 frame:0

TX packets:15 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000 

RX bytes:2031 (1.9 KiB)  TX bytes:2064 (2.0 KiB)

eth4      Link encap:Ethernet  HWaddr 00:0C:29:79:17:FA  

UP BROADCAST SLAVE MULTICAST  MTU:1500  Metric:1

RX packets:11 errors:0 dropped:0 overruns:0 frame:0

TX packets:12 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000 

RX bytes:1812 (1.7 KiB)  TX bytes:2105 (2.0 KiB)

Still the bond0 interface is UP and RUNNING fine.At the same time,”RUNNING” flag has disappear from eth4.

Now i have connected LAN cable back to eth4 and pulling out from eth2.

[root@mylinz2 Desktop]# ifconfig -a

bond0     Link encap:Ethernet  HWaddr 00:0C:29:79:17:FA  

inet addr:192.168.10.25  Bcast:192.168.10.255  Mask:255.255.255.0

inet6 addr: fe80::20c:29ff:fe79:17fa/64 Scope:Link

UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1

RX packets:22 errors:0 dropped:0 overruns:0 frame:0

TX packets:27 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:0 

RX bytes:3843 (3.7 KiB)  TX bytes:4169 (4.0 KiB)

eth2      Link encap:Ethernet  HWaddr 00:0C:29:79:17:FA  

UP BROADCAST SLAVE MULTICAST  MTU:1500  Metric:1

RX packets:11 errors:0 dropped:0 overruns:0 frame:0

TX packets:15 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000 

RX bytes:2031 (1.9 KiB)  TX bytes:2064 (2.0 KiB)

eth4      Link encap:Ethernet  HWaddr 00:0C:29:79:17:FA  

UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1

RX packets:11 errors:0 dropped:0 overruns:0 frame:0

TX packets:12 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000 

RX bytes:1812 (1.7 KiB)  TX bytes:2105 (2.0 KiB)

Still “bond0” interface running with UP & RUNNING flag.So you have successfully configured bonding on Redhat Linux 6.

To see complete bonding info,use below command.

[root@mylinz2 Desktop]# cat /proc/net/bonding/bond0 

Ethernet Channel Bonding Driver: v3.6.0 (September 26, 2009)

Bonding Mode: load balancing (round-robin)

MII Status: up

MII Polling Interval (ms): 0

Up Delay (ms): 0

Down Delay (ms): 0

Slave Interface: eth2

MII Status: up

Speed: 1000 Mbps

Duplex: full

Link Failure Count: 0

Permanent HW addr: 00:0c:29:79:17:fa

Slave queue ID: 0

Slave Interface: eth4

MII Status: up

Speed: 1000 Mbps

Duplex: full

Link Failure Count: 0

Permanent HW addr: 00:0c:29:79:17:04

Slave queue ID: 0

[root@mylinz2 Desktop]#

To verify the current bonding mode,use below command. 

[root@mylinz2 Desktop]# cat /sys/class/net/bond0/bonding/mode

balance-rr 0

You can modify the bonding mode by editing “mode” in the ifcfg-bond0  configuration file.

[root@mylinz2 Desktop]# cat /etc/sysconfig/network-scripts/ifcfg-bond0 |grep -i mode

BONDING_OPTS="mode=0 miimon=100"

POLICY DETAILS Ploicy Name Code Description balance-rr 0 Round-Robin policy for fault tolerance active-backup 1 Active-Backup policy for fault tolerance balance-xor 2 Exclusive-OR policy for fault tolerance broadcast 3 All transmissions are sent on all slave interfaces. 802.3ad 4 Dynamic link aggregation policy balance-tlb 5 Transmit Load Balancing policy for fault tolerance balance-alb 6 Active Load Balancing policy for fault tolerance

To list the currently configured bonds,

[root@mylinz2 Desktop]# cat /sys/class/net/bonding_masters 

bond0

How to configure SSL in vCenter 6.7

First take vCenter VM snapshot for backup purpose.

Take note of host where the vCenter VM resides while starting the activity.

Take Access of vCenter Shell to create a certificate CSR request.

root@prod-vcsa71 [ ~ ]# /usr/lib/vmware-vmca/bin/certificate-manager

Now copy the CSR file content in notepad file and save as .txt or .csr

Once have the CSR, generate a certificate by using this CSR.

Now copy the certificate file to the vcenter along with the RootCA certificate.

Start process for Import the certificate.

root@prod-vcsa71 [ ~ ]# /usr/lib/vmware-vmca/bin/certificate-manager

Provide certificate file location as per below the snip, Once all details provided it will take around 20-30 mins depending on the vCenter performance.

Once all required services started properly it will give the status as mentioned below.

Now try to access the vCenter from WebGUI, It is now secure.

Also try to access the vCenter Appliance Management Interface, It will still show the certificate error, to resolve this, restart the vami https service as mentioned below.

root@prod-vcsa71 [ /opt ]# /sbin/service vami-lighttpd restart

Now again try to access the vCenter Appliance Management Interface, It will also start with SSL certificate.

To check service status: 

root@prodvcenter [ ~ ]# service-control --status --all

To check logs if anything fails.

root@prodvcenter [ ~ ]# tail -f /var/log/vmware/vmcad/certificate-manager.log

If Certificate import files due to content-library service fails to start, increase Start time in below mentioned file from 300 to 600sec.

root@prodvcenter [ ~ ]# vi /etc/vmware/vmware-vmon/svcCfgfiles/vdcs.json

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How to Install or upgrade the VMWare Tools

1.    Select machine on which wants to install/upgrade the VMWare tools (Navigate to Summary > Install/Upgrade VMWare Tools)

     2. Select the Interactive Upgrade option and click on Upgrade.

    3. After upgrade selection you can see and verify the ISO image is connected as mentioned below.

   4. Now take access of machine and mount the attached ISO.

   # mount /dev/cdrom /mnt/

   5. Temporary copy the VMWareTools upgrade tar to local machine.

   # mkdir /tmp/vmware

   # cp VMwareTools-10.3.5-10430147.tar.gz /tmp/vmware/

   # cd /tmp/vmware/

   # tar xzvf VMwareTools-10.3.5-10430147.tar.gz

   # cd vmware-tools-distrib/

   # ./vmware-install.pl

   Press “Enter” on asked inputs.

   Once installed the tools successfully it will prompt the status of installed tool and its service status.

   6. Check the service status by below command.

   # /etc/vmware-tools/services.sh “status/start/stop”

   7. It will automatically eject the ISO file, if not then un-mount the ISO file manually and    disconnect/verify it from vCenter.

   8. Check and verify the status of VMware Tools from vCenter.

   9. Re-config the VMWare tools after each Kernel upgrades.

   # ./usr/bin/vmware-config-tools.pl

   VMware automatic kernel modules: yes

   10. Upgrade VMware Tools in Windows machines.

    Fist attach the ISO as mentioned in Points 1, 2 & 3.

    Take access of machine and open the CD/DVD, there you can see and run the VMware/setup.exe

    Follow the instructions for successfully installation/up gradation of tools.

    Restart the machine when prompted and disconnect the CD/DVD from vCenter.

    Verify the VMware Tools status from vCenter (As mentioned in point no. 8).