Turning Commands Into a Bash Script

In this hands-on lab, we’re going to write a shell script for connecting to Linux Academy Linux servers from another Linux (or Mac) host, without having to first accept the RSA fingerprint.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Determine What Options Should Be Used with the `ssh` Command

View the man page for the ssh command, and determine the option to use to disable host key checking.
```
man ssh
```

The syntax to use is:

ssh -o StrictHostKeyChecking=no user@host

Build a Script from the Required Commands

Create a bin folder in cloud_user‘s home directory.
```
mkdir bin
```
Use vim or nano to create the file lab.sh in the new bin folder.
```
vim bin/lab.sh
```
Start with the shebang at the top of the file.
```
#!/bin/bash
```
Add a line to ssh using the variable from above and taking the first parameter as the host address.
```
ssh -o StrictHostKeyChecking=no $login_user@$1
```
Add a line to set a variable for the login user.
```
login_user=cloud_user
```
Add two lines to make sure that that the first variable is not null and close the script.
```
if [ -n $1 ]
```
```
fi
```

The completed script should look like this

#!/bin/bash  

login_user=cloud_user
if [ -n $1 ]
then
  ssh -o StrictHostKeyChecking=no $login_user@$1
fi

Then save the file by running:
```
:wq!
```

Execute and Verify the Script

Save the file, and make it executable.
```
chmod u+x bin/lab.sh
```
Run the script, passing 10.0.1.10 as the first parameter to be assigned to $1.
```
./bin/lab.sh 10.0.1.10
```
Once prompted input the cloud_user‘s password.

Add the New `bin` Directory to the `PATH` Variable

Append to the .bashrc file in cloud_user‘s home directory to add the new bin folder to the PATH environment variable.
```
echo 'PATH="$HOME/bin:$PATH"' >> .bashrc
```
Source .bashrc to pick up the change.
```
source .bashrc
```
Verify that you can run lab.sh without specifying the path to the script.
```
lab.sh 10.0.1.10
```

What are Hands-on Labs

Hands-on Labs are real environments created by industry experts to help you learn. These environments help you gain knowledge and experience, practice without compromising your system, test without risk, destroy without fear, and let you learn from your mistakes. Hands-on Labs: practice your skills before delivering in the real world.

Turning Commands Into a Bash Script

About this Hands-on Lab

Learning Objectives

Additional Resources

What are Hands-on Labs

Newsletter