1. May 04, 2014 So rnd 1200 5000 5 will output 5 random numbers between 1200 and 5000. For whenever one needs some. No need to specify 1 if you need just one and you're in a hurry.
2. I want to add a user to the linux system from a script, but I don't want to invent or care for the password. This should be done automatically. The goal is to generate ssh-keys and this user need.
3. Aug 19, 2019 Using SSH keys for authentication is highly recommended, as a safer alternative to passwords. This tutorial will guide you through the steps on how to generate and set up SSH keys on CentOS 7. We also cover connecting to a remote server using the keys and disabling password authentication.
4. Use dd command to read data from /dev/random. Dd if=/dev/random of=random.dat bs=1000000 count=5000 That would read 5000 1MB blocks of random data, that is a whole 5 gigabytes of random data! Experiment with blocksize argument to get the optimal performance.
5. Quick script to generate new GPG keys (and export pertinent details) - gen-key.bash. # Send commands to set up the environment and then run the GPG command.
6. The question was 'How to generate a random string of a specific length' @DennisWilliamson, so while your comment is correct as such, it's not correct in the context of this question.

• Linux Server Set Up A Script To Generate Random Keys Free
• Linux Server Set Up A Script To Generate Random Keys Download

Introduction

Secure Shell (SSH) is an encrypted protocol used by Linux users to connect to their remote servers.

Aug 01, 2014 This tutorial provides an approach on how to set up Secure Sockets Layer (SSL) communication cryptographic protocol on Apache Web Server installed in Red Hat Enterprise Linux/CentOS 7.0, and generate self-signed Certificates and Keys with the help of a bash script which greatly simplifies the entire process. Step 1: Install and Configure Apache.

Generally, there are two ways for clients to access their servers – using password based authentication or public key based authentication.

Using SSH keys for authentication is highly recommended, as a safer alternative to passwords.

This tutorial will guide you through the steps on how to generate and set up SSH keys on CentOS 7. We also cover connecting to a remote server using the keys and disabling password authentication.

1. Check for Existing Keys

Prior to any installation, it is wise to check whether there are any existing keys on the client machines.

Open the terminal and list all public keys stored with the following command:

The output informs you about any generated keys currently on the system. If there aren’t any, the message tells you it cannot access /.ssh/id_*.pub , as there is no such file or directory.

2. Verify SSH is Installed

To check if thw package is installed, run the command:

If you already have SSH, the output tells you which version it is running. Currently, the latest version is OpenSSH 8.0/8.0p1.

Note: Refer to our guide If you need to install and enable SSH on your CentOS system.

Steps to Creating SSH keys on CentOS

1. Start by logging into the source machine (local server) and creating a 2048-bit RSA key pair using the command:

If you want to tighten up security measures, you can create a 4096-bit key by adding the -b 4096 flag:

2. After entering the command, you should see the following prompt:

3. To save the file in the suggested directory, press Enter. Alternatively, you can specify another location.

Note: If you already have a key pair in the proposed location, it is advisable to pick another directory. Otherwise it will overwrite existing SSH keys.

4. Next, the prompt will continue with:

Although creating a passphrase isn’t mandatory, it is highly advisable.

5. Finally, the output will end by specifying the following information:

Now you need to add the public key to the remote CentOS server.

You can copy the public SSH key on the remote server using several different methods:

1. using the ssh-copy-id script
2. using Secure Copy (scp)
3. manually copying the key

The fastest and easiest method is by utilizing ssh-copy-id. If the option is available, we recommend using it. Otherwise, try any of the other two noted.

1. Start by typing the following command, specifying the SSH user account, and the IP address of the remote host:

If it is the first time your local computer is accessing this specific remote server you will receive the following output:

2. Confirm the connection – type yes and hit Enter.

3. Once it locates the id_rsa.pub key created on the local machine, it will ask you to provide the password for the remote account. Type in the password and hit Enter.

4. Once the connection has been established, it adds the public key on the remote server. This is done by copying the ~/.ssh/id_rsa.pub file to the remote server’s ~/.ssh directory. You can locate it under the name authorized_keys.

5. Lastly, the output tells you the number of keys added, along with clear instructions on what to do next:

1. First, set up an SSH connection with the remote user:

2. Next, create the ~/.ssh directory as well as the authorized_keys file:

3. Use the chmod command to change the file permission:

chmod 700 makes the file executable, while chmod 600 allows the user to read and write the file.

4. Now, open a new terminal session, on the local computer.

5. Copy the content from id_rsa.pub (the SSH public key) to the previously created authorized_keys file on the remote CentOS server by typing the command:

With this, the public key has been safely stored on the remote account.

1. To manually add the public SSH key to the remote machine, you first need to open the content from the ~/.ssh/id_rsa.pub file:

2. As in the image below, the key starts with ssh-rsa and ends with the username of the local computer and hostname of the remote machine:

3. Copy the content of the file, as you will need later.

4. Then, in the terminal window, connect to the remote server on which you wish to copy the public key. Azure api management generate subscription key. Use the following command to establish the connection:

5. Create a ~/.ssh directory and authorized_keys file on the CentOS server with the following command:

6. Change their file permission by typing:

7. Next, open the authorized_keys file with an editor of your preference. For example, to open it with Nano, type:

8. Add the public key, previously copied in step 2 of this section, in a new line in (under the existing content).

9. Save the changes and close the file.

10. Finally, log into the server to verify that everything is set up correctly.

Once you have completed the previous steps (creating an RSA Key Pair and copying the Public Key to the CentOS server), you will be able to connect to the remote host without typing the password for the remote account.

All you need to do is type in the following command:

Linux Server Set Up A Script To Generate Random Keys Free

If you didn’t specify a passphrase while creating the SSH key pair, you will automatically log in the remote server.

Otherwise, type in the passphrase you supplied in the initial steps and press Enter.

Once the shell confirms the key match, it will open a new session for direct communication with the server.

Although you managed to access the CentOS server without having to provide a password, it still has a password-based authentication system running on the machine. This makes it a potential target for brute force attacks.

You should disable password authentication entirely by following the outlined steps.

Note: Consider performing the following steps through a non-root account with sudo privileges, as an additional safety layer.

1. Using the SSH keys, log into the remote CentOS server which has administrative privileges:

2. Next, open the SSH daemon configuration file using a text editor of your choice:

3. Look for the following line in the file:

4. Edit the configuration by changing the yes value to no. Thus, the directive should be as following:

5. Save the file and exit the text editor.
6. To enable the changes, restart the sshdservice using the command:

7. Verify the SSH connection to the server is still functioning correctly. Open a new terminal window and type in the command:

In this article, you learned how to generate SSH key pairs and set up an SSH key-based authentication. We also covered copying keys to your remote CentOS server, and disabling SSH password authentication.

Next, You Should Read:

Terraform allows you to define and create complete infrastructure deployments in Azure. You build Terraform templates in a human-readable format that create and configure Azure resources in a consistent, reproducible manner. This article shows you how to create a complete Linux environment and supporting resources with Terraform. You can also learn how to install and configure Terraform.

Note

For Terraform specific support, please reach out to Terraform directly using one of their community channels:

• The Terraform section of the community portal contains questions, use cases, and useful patterns.

• For provider-related questions please visit the Terraform Providers section of the community portal.

Create Azure connection and resource group

Let's go through each section of a Terraform template. You can also see the full version of the Terraform template that you can copy and paste.

The provider section tells Terraform to use an Azure provider. To get values for subscription_id, client_id, client_secret, and tenant_id, see Install and configure Terraform.

Tip

If you create environment variables for the values or are using the Azure Cloud Shell Bash experience , you don't need to include the variable declarations in this section.

The following section creates a resource group named myResourceGroup in the eastus location:

In additional sections, you reference the resource group with ${azurerm_resource_group.myterraformgroup.name}.

Create virtual network

The following section creates a virtual network named myVnet in the 10.0.0.0/16 address space:

The following section creates a subnet named mySubnet in the myVnet virtual network:

Create public IP address

To access resources across the Internet, create and assign a public IP address to your VM. The following section creates a public IP address named myPublicIP:

Create Network Security Group

Network Security Groups control the flow of network traffic in and out of your VM. The following section creates a network security group named myNetworkSecurityGroup and defines a rule to allow SSH traffic on TCP port 22:

Create virtual network interface card

A virtual network interface card (NIC) connects your VM to a given virtual network, public IP address, and network security group. The following section in a Terraform template creates a virtual NIC named myNIC connected to the virtual networking resources you've created:

Create storage account for diagnostics

To store boot diagnostics for a VM, you need a storage account. These boot diagnostics can help you troubleshoot problems and monitor the status of your VM. The storage account you create is only to store the boot diagnostics data. As each storage account must have a unique name, the following section generates some random text:

Now you can create a storage account. The following section creates a storage account, with the name based on the random text generated in the preceding step:

Create virtual machine

The final step is to create a VM and use all the resources created. The following section creates a VM named myVM and attaches the virtual NIC named myNIC. The latest Ubuntu 16.04-LTS image is used, and a user named azureuser is created with password authentication disabled.

SSH key data is provided in the ssh_keys section. Provide a public SSH key in the key_data field.

Complete Terraform script

To bring all these sections together and see Terraform in action, create a file called terraform_azure.tf and paste the following content:

Build and deploy the infrastructure

With your Terraform template created, the first step is to initialize Terraform. This step ensures that Terraform has all the prerequisites to build your template in Azure.

The next step is to have Terraform review and validate the template. This step compares the requested resources to the state information saved by Terraform and then outputs the planned execution. The Azure resources aren't created at this point.

After you execute the previous command, you should see something like the following screen:

If everything looks correct and you're ready to build the infrastructure in Azure, apply the template in Terraform:

Once Terraform completes, your VM infrastructure is ready. Obtain the public IP address of your VM with az vm show:

Linux Server Set Up A Script To Generate Random Keys Download

You can then SSH to your VM:

Next steps