login – A Passionate Techie

openvpn pam authentication failure

Error:

AUTH-PAM: BACKGROUND: user 'paul' failed to authenticate: System error
Sun Mar 13 16:41:02 2016 86.137.55.234:49377 PLUGIN_CALL: plugin
function PLUGIN_AUTH_USER_PASS_VERIFY failed with status 1:
/etc/openvpn/openvpn-plugin-auth-pam.so

Solution:

On the openvpn server install saslauthd

# aptitude install sasl2-bin

Start the daemon

# saslauthd -d -a pam -m /var/run/saslauthd/

Make simple authentication

# testsaslauthd -u paul -p 1234567 -s login

The result must be

0: OK "Success."

unable to login to a virtual machine

If you want to add a user to a virtual machine without logging into it or change the password of root or any other user, you can use virt-customize.

The virt-customize command-line tool can be used to customize a virtual machine. For example, by installing packages and editing configuration files.

To use virt-customize, the guest virtual machine must be offline, so you must shut it down before running the commands. Note that virt-customize modifies the guest or disk image in place without making a copy of it. If you want to preserve the existing contents of the guest virtual machine, you must snapshot, copy or clone the disk first.

To install virt-customize, run one of the following commands:

sudo yum install libguestfs-tools-c

sudo apt-get install libguestfs-tools

Please follow the below-mentioned steps:

a. Add a new user:

virt-customize -a centos.img --run-command "adduser user1"

virt-customize -a centos.img --ssh-inject user1:string:<YOUR PUBLICKEY STRING HERE>

Now you can login with user1 and public-key
If you want passwordless sudo access execute the following:

virt-customize -a centos.img --run-command "echo 'user1 ALL=(ALL) NOPASSWD: ALL' >> /etc/sudoers.d/user1-sudo"

b. Change root password:

virt-customize -a centos.img --root-password password:mypass

You can login to the VM with root/mypass

c. Change password of non-root user:

virt-customize -a centos.img --password user1:password:mypass2

You can login to the VM with user1/mypass2

Heroku: Couldn’t find that app

To troubleshoot this issue firstly check the heroku logs with command:
heroku logs -tail

Check for the error here,

Make sure you have logged into heroku with:
heroku auth:login

Check the list of apps in heroku with:
heroku apps

make sure you have initialized the git repository in the directory where your code is and not it’s parent or sub directory.
You can initialize it with git init

Add the files with git add .

Commit the files with git commit -m “Your message”

Add the remote git into heroku with:
heroku git:remote -a app-name

You can manually add the heroku git remote repository with the comand:
git remote add heroku git@heroku.com:arati.git

Check the remote with git remote -v

You can add ssh keys for heroku with command heroku keys:add
It will create ssh keys in .ssh folder of your home directory. Make sure you have ssh-keygen in your path otherwise you’ll be getting an error as: ‘ENOENT’: spawn ssh-keygen ENOENT

You should be able to push your code with: git push heroku master

Create public key from .pem

Execute the following command:
ssh-keygen -y -f /tmp/key.pem > key.pub

How to prevent a user from login in, but allow “su – user” in Linux?

You can use AllowUsers / AllowGroups if you have only a few users/groups that are allowed to login via ssh or DenyUsers / DenyGroups if you have only a few users/groups that are not allowed to login. Note that this only restricts login via ssh, other ways of login (console, ftp, …) are still possible. You need to add these options to your /etc/ssh/sshd_config file for most ssh installations.

If you have set the login shell to /bin/false you can use su -s /bin/bash user (replace /bin/bashwith the shell of your choice)

Change to jenkins user

Look at the shell specified in /etc/passwd for the jenkins user. You can do so by running something like:

grep jenkins /etc/passwd

The output will look similar to this:

jenking:1001:1001::/usr/local/jenkins:/bin/false

The last field is the login shell of the user. Here you can see it is set to /bin/false which will immediately exit.

The solution is to specify which shell to use as you described:

su -s /bin/bash jenkins

Or modify the login shell of the jenkins user with “usermod(8)” (executed as a root user) :

usermod -s /bin/bash jenkins

Then grep jenkins /etc/passwd should now output something like:

jenkins:1001:1001::/usr/local/jenkins:/bin/bash

After which. su - jenkins will work as you expect.

How to pass environment variable to sudo su

You can do it without calling login shell:

sudo DUMMY=dummy su <username> -c 'echo "$DUMMY"'

How to add multiple SSH keys to single machine

Generate keys with the command:

ssh-keygen -t rsa

Then add the public key to the authorized_keys with the command:

cat .ssh/new_key.pub >> ~/.ssh/authorized_keys

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