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Configure Network in CentOS / RHEL from command line

May 31, 2018 Leave a comment

How many of you are aware of a text user interface for network configuration ?. A tool called NMTUI (Network Manager Text User Interface) is available in CentOS and Redhat systems. You can simply open this by typing nmtui in the command line.

If this command is not available, you have to install the NetworkManager-tui package.

yum install NetworkManager-tui

If you type nmtui command in command line, the following console will open up. You can configure the network configurations in the opened console. You can

nmtui

nmtui

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Disable Sleep mode in CentOS7/RHEL7 laptop on lid close

May 30, 2018 Leave a comment

The following tip will help you to disable the powersaving or sleep mode behavior of your CentOS or RHEL laptop or desktop. If GUI is present, the following steps will help.

Applications => Utilities => Tweak Tool => Shell => Don't suspend on lid close => ON

But if GUI is not installed, then the only option is to disable this from the commandline. It is very easy, don’t worry. Who cares about the GUI in Linux. ? 🙂 (I love the black screen)

Open /etc/systemd/logind.conf, then make edit in the following configuration. By default, the value of this config will be suspend

HandleLidSwitch=ignore

man logind.conf will provide the complete details about this configuration file. Hope this tip helps.

 

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How to check the Java architecture from command line ?

August 30, 2017 Leave a comment

To check the Java architecture whether it is 32 bit or 64 bit, the following commands will be helpful.

Execute the following commands in the command line and check the results

java -d32 -version

java -d64 -version

If any of the above command is giving an error message similar to “Error: This Java instance does not support a xx-bit JVM.” If it is not supporting 32 bit, then we can say it is a 64 bit Java. If it is not supporting 64 bit, we can say it is a 32-bit Java. The screenshot of the same is attached below.

java_screen.PNG

Hope this will help .. 🙂

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Get public and private IP address of an EC2 instance from the command line

July 24, 2017 Leave a comment

Sometimes we may get requirements to identify the public ip address of an ec2 instance from the command line. There are various ways to perform this operation.

  1. Using AWS CLI
  2. Using a simple REST call
aws ec2 describe-instances --instance-ids  --query 'Reservations[*].Instances[*].PublicIpAddress' --output text

If we are on the same EC2 host, we can obtain the details of the EC2 instance using the instance metadata service.

curl http://169.254.169.254/latest/meta-data/


ami-id
ami-launch-index
ami-manifest-path
block-device-mapping/
hostname
iam/
instance-action
instance-id
instance-type
local-hostname
local-ipv4
mac
metrics/
network/
placement/
profile
public-hostname
public-ipv4
public-keys/
reservation-id
security-groups
services/

Using this, for getting the private IP, the command will be

curl http://169.254.169.254/latest/meta-data/local-ipv4

For getting the public IP, the command will be

curl http://169.254.169.254/latest/meta-data/public-ipv4

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