2.2. Preparing a managed node

Procedure

1. Create a user named ansible:

   [root@managed-node-01]# useradd ansible

   The control node later uses this user to establish an SSH connection to this host.

2. Set a password for the ansible user:

   [root@managed-node-01]# passwd ansible
   Changing password for user ansible.
   New password: <password>
   Retype new password: <password>
   passwd: all authentication tokens updated successfully.

   You must enter this password when Ansible uses sudo to perform tasks as the root user.

3. Install the ansible user’s SSH public key on the managed node:

   1. Log in to the control node as the ansible user, and copy the SSH public key to the managed node:

      [ansible@control-node]$ ssh-copy-id managed-node-01.example.com
      /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/ansible/.ssh/id_rsa.pub"
      The authenticity of host 'managed-node-01.example.com (192.0.2.100)' can't be established.
      ECDSA key fingerprint is SHA256:9bZ33GJNODK3zbNhybokN/6Mq7hu3vpBXDrCxe7NAvo.

   2. When prompted, connect by entering yes:

      Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
      /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
      /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys

   3. When prompted, enter the password:

      ansible@managed-node-01.example.com's password: <password>
      
      Number of key(s) added: 1
      
      Now try logging into the machine, with:   "ssh 'managed-node-01.example.com'"
      and check to make sure that only the key(s) you wanted were added.

   4. Verify the SSH connection by remotely executing a command on the control node:

      [ansible@control-node]$ ssh managed-node-01.example.com whoami
      ansible

4. Create a sudo configuration for the ansible user:

   1. Create and edit the /etc/sudoers.d/ansible file by using the visudo command:

      [root@managed-node-01]# visudo /etc/sudoers.d/ansible

      The benefit of using visudo over a normal editor is that this utility provides basic checks, such as for parse errors, before installing the file.

   2. Configure a sudoers policy in the /etc/sudoers.d/ansible file that meets your requirements, for example:

      • To grant permissions to the ansible user to run all commands as any user and group on this host after entering the ansible user’s password, use:

        ansible   ALL=(ALL) ALL

      • To grant permissions to the ansible user to run all commands as any user and group on this host without entering the ansible user’s password, use:

        ansible   ALL=(ALL) NOPASSWD: ALL

   Alternatively, configure a more fine-granular policy that matches your security requirements. For further details on sudoers policies, see the sudoers(5) manual page.

Verification

1. Verify that you can execute commands from the control node on an all managed nodes:

   [ansible@control-node]$ ansible all -m ping
   BECOME password: <password>
   managed-node-01.example.com | SUCCESS => {
       	...
       	"ping": "pong"
   }
   ...

   The hard-coded all group dynamically contains all hosts listed in the inventory file.

2. Verify that privilege escalation works correctly by running the whoami utility on a managed host by using the Ansible command module:

   [ansible@control-node]$ ansible managed-node-01.example.com -m command -a whoami
   BECOME password: <password>
   managed-node-01.example.com | CHANGED | rc=0 >>
   root

   If the command returns root, you configured sudo on the managed nodes correctly.