Using SSH, Redirection, and Permissions in Linux

30 minutes
  • 4 Learning Objectives

About this Hands-on Lab

In this lab, we’ll go over I/O redirection, file permissions, and using the `ssh` tool. These are skills that will serve you well in your career as a Linux sysadmin. Once complete, you’ll have a solid understanding of how to use these tools.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Enable SSH to Connect Without a Password from the `dev` User on `server1` to the `dev` User on `server2`

We need to use SSH keys to satisfy this requirement, so generate them with this:

 [dev@server1]$ ssh-keygen

Then run:

 [dev@server1]$ ssh-copy-id <server2 IP>
Copy All tar Files from `/home/dev/` on `server1` to `/home/dev/` on `server2`, Extract Them, and Redirect Output to `/home/dev/tar-output.log`

We need to use a method of copying files over a network. scp is the best tool, like this:

[dev@server1]$ scp *.gz <server2 IP>:~/

Then connect to server2 using ssh:

[dev@server1]$ ssh <server2_IP>

Then we can extract the files:

[dev@server2]$ tar -xvf deploy_content.tar.gz >> tar-output.log
[dev@server2]$ tar -xvf deploy_script.tar.gz >> tar-output.log

Make sure to use >>, so that the output is appended rather than overwritten.

Set the Umask So That New Files Are Only Readable and Writeable by the Owner

The task is asking to make new files with the following permission: 0600.

So we can do subtraction to figure out what our umask should be.

0666 <– Default

0600 <– Desired

----

0066 <– What we need to set

So we run:

[dev@server2]$ umask 0066
Verify the `/home/dev/deploy.sh` Script Is Executable and Run It

First, we check permissions on deploy.sh:

 [dev@server2]$ ls -l deploy.sh

There’s no execute bit. Let’s add one:

 [dev@server2]$ chmod +x deploy.sh

And then run it:

 [dev@server2]$ ./deploy.sh

Additional Resources

We need to set up a new server for a developer to use. He needs to be able to connect with ssh from server1 to server2 as the dev user, without having to enter a password password.

Once that's set up there are some tar files on server1 that need to be copied over and extracted. To enable the developer to verify that it was done correctly, we should have all the output from the extraction go to /home/dev/tar-output.log.

We need to make sure that new files have the correct permissions (readable and writeable by only the user) by setting the umask correctly.

Once complete we should verify permissions on the very important /home/dev/deploy.sh script and run it.

Log in to one of the servers (which will then be referred to as server1 throughout the rest of the lab) using the credentials provided:

ssh dev@<server1_PUBLIC_IP>

The password for the dev user is the same as for cloud_user.

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.

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