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Disable auto restart policy of docker container

April 18, 2018 Leave a comment

If a docker container is started with –restart=always, then the container will not allow you to stop it.  We can change this behavior by modifying the restart policy. Refer the docker  official documentation for more info

For example

docker run -d --restart=always -p 80:80 -it nginx

To modify this behavior, try the following command.

docker update --restart=no your-container

Another option that allows us to stop the container manually is

docker update --restart=unless-stopped your-container
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Filed under docker, Linux World, Tips and Tricks Tagged with , , , , , , , , , , ,

How to verify whether a private key matches with the SSL certificate ?

January 23, 2018 Leave a comment

This is a very common question that comes to our mind while setting up SSL in our applications. How to verify whether the key matches with the SSL certificate ?

A very easy way to verify that is given below.

We need to compare the modulus of the certificate against the modulus of the private key.

Execute the below command to get the modulus of a certificate.

openssl x509 -noout -modulus -in mycertificate.crt | openssl md5

This will generate the modulus something like e091f305089662689d62126d49910031 

Execute the below command to get the modulus of a private key.

openssl rsa -noout -modulus -in mykey.key | openssl md5

This will generate the modulus of the private key. You should get the key modulus as same as certificate modulus above. i.e e091f305089662689d62126d49910031

If both the modulus are same, we can say that the certificate and the key are matching.

Filed under Tips and Tricks Tagged with , , , , , , ,

Common dependencies to install PyCrypto package in CentOS/RHEL

November 15, 2017 Leave a comment

The installation of pycrypto package may fail with errors like

“error: no acceptable C compiler found in $PATH”

“RuntimeError: autoconf error”

“fatal error: Python.h: No such file or directory”

” #include “Python.h”
^
compilation terminated.
error: command ‘gcc’ failed with exit status 1″

The solution for this issue is to install the following dependent packages.

yum install gcc

yum install gcc-c++

yum install python-devel

pip install pycrypto

Filed under Tips and Tricks Tagged with , , , , , , , , ,

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 .. 🙂

Filed under Tips and Tricks Tagged with , , , , , , , , ,

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

Filed under cloud, Linux World, Tips and Tricks Tagged with , , , , , , , , , , , ,

(13)Permission denied: access to /index.html denied

May 22, 2017 Leave a comment

I was getting the error “(13)Permission denied: access to /index.html denied” after deploying a static website in Apache webserver.

Solution:

Apache could not access those directories because of the SELinux security settings. Execute the below command

chcon -R -t httpd_sys_content_t  

 

Filed under Tips and Tricks

Python code to list all the running EC2 instances across all regions in an AWS account

March 9, 2017 12 Comments

This code snippet will help you to get the list of all running EC2 instances across all regions in an AWS account. I have used python boto3 package for developing the code. This code will dynamically pick up all the aws ec2 regions. So the code will work perfectly without any modification even if a new region gets added to the AWS.

Note: Only the basic api calls just to list the instance details are mentioned in this program . Proper coding convention is not followed . 🙂

Filed under BigData World, Tips and Tricks Tagged with , , , , , , , , , ,

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