Generate Ssh Key Rhel 6

Generate Ssh Key Rhel 7
Generate Ssh Key Linux Redhat

I need to automate ssh-keygen -t rsa with out a password i.e. Enter at the prompt. On RHEL 6, I got this error: 'ssh-keygen. How to generate public key from. Jun 06, 2014 Generate SSH Key Pair on CentOS SSH (Secure Shell) and SFTP (Secure FTP) support a very strong security model that can be used instead of the normal username and password authentication scheme. Generate Your Keys. Red Hat Enterprise Linux 6 uses SSH Protocol 2 and RSA keys by default (see Section 14.1.3, “Protocol Versions” for more information). Important Do not generate key pairs as root, as only root would be able to use those keys.

am a new RHEL 8 server sysadmin. How do I configure SSH public key-based authentication for RHEL (Red Hat Enterprise Linux) 8 server?
Introduction – SSH is an acronym for secure shell. It is a suite of cryptographic network protocol. It allows users to log in and transfer files securely over the unsecure network such as the Internet. OpenSSH is an implementation of SSH protocol on RHEL 8. You can log in using RHEL 8 user and password account. However, OpenSSH project recommends log in using a combination of a private and public SSH keys.

Sample set up for our RHEL 8 server

Where,

You generate a key pair on your Linux/Unix/macOS desktop.
Place the public key on RHEL 8 server.
One can unlock public key using a private key stored on your desktop with the help of ssh command.
When both the public and private key correct you can log in without a password.

How do I set up SSH keys on RHEL 8 server?

The procedure to set up SSH key on Red Hat Enteprise Linux 8 server:

On your local desktop type:
ssh-keygen
Install public key into remote RHEL 8 server using:
ssh-copy-id user@remote-RHEL8-server-ip
Use ssh for password less login:
ssh user@remote-RHEL8-server-ip

Let us see all commands and steps in details.

How to create the ed25519 or RSA key pair

The syntax is:
ssh-keygen -t ed25519 ssh-keygen -t rsa ssh-keygen -t rsa -b 4096 -f ~/.ssh/aws-lighsail.key -C 'My AWS SSH Keys' ssh-keygen -t ed25519 -f ~/.ssh/linode-usa-www1-vps.key -C 'My Linode SSH Keys for www'
Where,

Get the API key. You must have at least one API key associated with your project. To get an API key: Visit the Google Cloud Platform Console. Click the project drop-down and select or create the project for which you want to add an API key. Click the menu button and select APIs & Services Credentials. On the Credentials page, click Create credentials API key. Google map api android studio. A key with this name can be used to authenticate to multiple Google Maps-based APIs on the Android platform, including the Google Maps Platform Premium Plan. For backwards compatibility, the API. To get an API key: Visit the Google Cloud Platform Console. Click the project drop-down and select or create the project for which you want to add an API key. Click the menu button and select APIs & Services Credentials. On the Credentials page, click Create credentials API key.

-t rsa OR -t ed25519 : Specifies the type of key to create. The possible values “dsa”, “ecdsa”, “ed25519”, or “rsa” for SSH protocol version 2.
-b 4096 : Specifies the number of bits in the key to create.
-f~/.ssh/aws-lighsail.key : Specifies the filename of the key file.
-C -C 'My AWS SSH Keys' : Set a new comment.

I am going type the following command on my Ubuntu desktop to create the key pair:
$ ssh-keygen -t ed25519
Modo 3d. I strongly recommend that you set up a passphrase when prompted.

How to copy the public key

Now our key paid generated and stored in ~/.ssh/ directory. You must copy a public SSH key file named ~/.ssh/id_ed25519.pub (or ~/.ssh/id_rsa.pub if you created RSA key) to the RHEL 8 server. Try the ssh-copy-id command as follows:
$ ssh-copy-id -i ~/.ssh/fileNameHere.pubuser@remote-RHEL8-server-ip
For example:
$ ssh-copy-id -i ~/.ssh/id_ed25519.pub vivek@192.168.2.211

Generate Ssh Key Rhel 7

How to log in using ssh and without a password

Now try logging into the machine, with the ssh command as follows:
$ ssh user@rhel-8-server $ ssh vivek@192.168.2.211
You should be able to log in without a password. If you set up a passphrase, unlock it as follows for your current session so that you don’t have to enter it every time you run ssh, sftp, scp, rsync and other commands:
$ ssh-agent $SHELL $ ssh-add

Optional settings for root user

Disable root user log in all together on RHEL 8 via ssh. Log in as root user on RHEL 8 and run following to add a user named vivek to wheel group:
# usermod -aG wheel vivek # id vivek
Allows users in group wheel can use sudo command to run all commands on RHEL 8 server. Next disable root user login by adding the following line to sshd_config:
# vi /etc/ssh/sshd_config
Disable the password for root login and only allow ssh keys based login:

Save and close the file. Reload the ssh server:
# systemctl reload sshd.service
For more info see “Top 20 OpenSSH Server Best Security Practices“.

Conclusion

You learned how to set up and use SSH keys to manage your RHEL 8 based server. For more info see OpenSSH man pages here.

12 Steps total

Step 1: Stop the Logging Services

You’re going to all this trouble to create a clean deployable template, so you might as well stop writing new data. Otherwise all your deployed VMs will have a log of you shutting the VM down.

Issue the following commands to stop the logging services:

/sbin/service rsyslog stop
/sbin/service auditd stop

Step 2: Remove any old kernels

You need yum-utils installed to get package-cleanup. This has to go before the yum cleanup in the next step as it needs your channel data. I usually let the post-deployment configuration management take care of this, but this is nice when we create a new template for a intermediate/point release, or just to cover a security hole.

Issue the following command to remove the old kernels (if there are any):

package-cleanup --oldkernels --count=1

Step 3: Clean out Yum

Yum keeps a cache in /var/cache/yum that can grow quite large, especially after applying patches to the template. For example, my lab host currently has 360 MB of stuff in yum’s cache right now, just from a few months of incremental patching. In the interest of keeping my template as small as possible I wipe this.

Generate Ssh Key Linux Redhat

Issue the following command to clean the cache:

yum clean all

Step 4: Force the logs to rotate and remove old logs we don’t need

Starting fresh with the logs is nice. It means that you don’t have old, irrelevant log data on all your cloned VMs. It also means that your template image is smaller. Change out the “rm” command for one that matches whatever your logrotate renames files as. As an aside, because people usually neglect this step, if you get really, really bored it’s fun to look at the old log data people leave on virtual appliances in cloud templates. Lots of leaked information there ;)

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Issue the following commands to clear the logs:

/usr/sbin/logrotate –f /etc/logrotate.conf
/bin/rm –f /var/log/*-???????? /var/log/*.gz
/bin/rm -f /var/log/dmesg.old
/bin/rm -rf /var/log/anaconda

Step 5: Truncate the audit logs (and other logs we want to keep placeholders for)

This whole /dev/null business is a neat function that lets you clear a file without restarting the process associated with it, useful in many more situations than just template-building.

Issue the following commands to truncate the audit logs:

/bin/cat /dev/null > /var/log/audit/audit.log
/bin/cat /dev/null > /var/log/wtmp
/bin/cat /dev/null > /var/log/lastlog
/bin/cat /dev/null > /var/log/grubby

Step 6: Remove the udev persistent device rules

Have you ever noticed that if you clone/deploy a Linux VM that won't bring up it single network interface and renames the interface to something like eth1? Yep, well that's the udev persistent network interface rules coming back to haunt you. This is how I've decided to deal with the problem.

This generally affects CentOS /RHEL 6 and you shouldn't have to do it in v7 but it won't hurt anything.

Issue the following command to remove the udev persistent rules:

/bin/rm -f /etc/udev/rules.d/70*

Step 7: Remove the traces of the template MAC address and UUIDs

This is a corollary to step 5, just removing unique identifiers from the template so the cloned VM gets its own. You can also change the “-i” to “-i.bak” if you want to keep a backup copy of the file.

Issue the following command to clear the identifiers:

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/bin/sed -i ‘/^(HWADDR|UUID)=/d’ /etc/sysconfig/network-scripts/ifcfg-e*

Step 8: Clean /tmp out

Under normal, non-template circumstances you really don’t ever want to run rm on /tmp like this. Use tmpwatch or any other manner of safer ways to do this, since there are attacks people can use by leaving symlinks and what-not in /tmp that rm might traverse (“whoops, I don’t have an /etc/passwd anymore!”). Plus, users and processes might actually be using /tmp, and it’s impolite to delete their files. However, this is your template image, and if there are people attacking your template you should reconsider how you’re doing business really.

/bin/rm –rf /tmp/*
/bin/rm –rf /var/tmp/*

Step 9: Remove the SSH host keys

If you don’t do this all your VMs will have all the same keys, which has negative security implications. It’s also annoying to fix later when you’ve realised that you’ve deployed a couple of years worth of VMs and forgot to do this in your prep script. Not that I would know anything about that. Nope.

/bin/rm –f /etc/ssh/*key*

Step 10: Remove the root user’s shell history

No sense in keeping this history around, it’s irrelevant to the cloned VM.

/bin/rm -f ~root/.bash_history
unset HISTFILE

Step 11: Remove the root user’s SSH history and other stuff

You might choose to just remove ~root/.ssh/known_hosts if you have SSH keys you want to keep around.

/bin/rm -rf ~root/.ssh/
/bin/rm -f ~root/anaconda-ks.cfg

Step 12: Clear bash history and shutdown for template creation

Time to clear the history of everything you've just done and shutdown the server in a clean state for converting to a VM:

history –c
sys-unconfig

The server will automatically now shutdown.

So that’s my prep routine. It relies heavily on keeping the rest of the VM clean, and only cleans up what we can’t avoid sullying. Once the server shuts down as a result of the sys-unconfig command you can convert to a sanitized template in vSphere and add any customization specs required to the Linux deployments.

3 Comments

Poblano
MasterChewie74 Aug 28, 2018 at 10:31pm
Hey Liam,
Awesome How To article! It really helped me out with a project I'm working on! If it's alright, I do have one question about doing the deployments from a template. I'm currently working with SUSE Enterprise Linux 12 and I noticed that when I deploy off a template, the /sda1 and /sda2 UUIDs are the same in every clone. Is this something that I need to change? Or can several servers with the same device UUIDs exist? If I need to change them, how should I go about it?
Thank you in advance for any and all help you may be able to provide!!!
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Pimiento
spicehead-gvo1u Sep 17, 2018 at 03:48am
MC, I blieve you will want to place this in your cleanup script:
echo '> Remove the traces of the template MAC address and UUIDs'
sudo sed -i '/^(HWADDR|UUID)=/d' /etc/sysconfig/network-scripts/ifcfg-e*
Hope this helps.
Sonora
sibzz Jan 10, 2019 at 06:24am
Great guide. Step 6 was specially interesting for me . That udev trick is very neat. Will be using it from now on.

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