View source for Adding a User to Your VM

{{DISPLAYTITLE:VM User Management and SSH Key Setup}}

== Quick Reference ==

Guide for adding users to VMs and configuring SSH key authentication.

== Add User to VM ==

<source lang="bash">
# Create user with home directory
sudo useradd -m -s /bin/bash username

# Set password
sudo passwd username

# Add to sudo group (if needed)
sudo usermod -aG sudo username
</source>

== Setup SSH Key ==

<source lang="bash">
# Create SSH directory
sudo mkdir -p /home/username/.ssh
sudo chmod 700 /home/username/.ssh
sudo chown username:username /home/username/.ssh

# Add public key
echo "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABgQC... user@hostname" | sudo tee /home/username/.ssh/authorized_keys
sudo chmod 600 /home/username/.ssh/authorized_keys
sudo chown username:username /home/username/.ssh/authorized_keys
</source>

== Complete Setup Script ==

For convenience, here's a complete script that automates the user creation and SSH key setup:

<source lang="bash">
#!/bin/bash

# VM User Management Script
# Usage: ./add_user.sh username "Full Name" "ssh-public-key"

if [ $# -ne 3 ]; then
    echo "Usage: $0 username 'Full Name' 'ssh-public-key'"
    exit 1
fi

USERNAME=$1
FULL_NAME=$2
SSH_PUBLIC_KEY=$3

echo "Creating user: $USERNAME"

# Create user account
sudo useradd -m -s /bin/bash -c "$FULL_NAME" $USERNAME

# Create SSH directory
sudo mkdir -p /home/$USERNAME/.ssh
sudo chmod 700 /home/$USERNAME/.ssh
sudo chown $USERNAME:$USERNAME /home/$USERNAME/.ssh

# Add SSH public key
echo "$SSH_PUBLIC_KEY" | sudo tee /home/$USERNAME/.ssh/authorized_keys
sudo chmod 600 /home/$USERNAME/.ssh/authorized_keys
sudo chown $USERNAME:$USERNAME /home/$USERNAME/.ssh/authorized_keys

# Copy default shell files
sudo cp /etc/skel/.bashrc /home/$USERNAME/
sudo cp /etc/skel/.profile /home/$USERNAME/
sudo chown $USERNAME:$USERNAME /home/$USERNAME/.bashrc /home/$USERNAME/.profile

echo "User $USERNAME created successfully!"
echo "SSH key configured. User can now connect via SSH."
</source>

== User Management Best Practices ==

=== Security Considerations ===

* Always use SSH key authentication instead of passwords when possible
* Regularly review and audit user accounts
* Remove access for users who no longer need it
* Use strong, unique SSH keys
* Consider implementing key rotation policies

=== Account Maintenance ===

<source lang="bash">
# List all users
cat /etc/passwd | grep -E "/bin/(bash|sh)$"

# Check user login history
last username

# Disable user account (lock)
sudo usermod -L username

# Remove user account (with home directory)
sudo userdel -r username
</source>

=== SSH Key Management ===

<source lang="bash">
# List authorized keys for a user
sudo cat /home/username/.ssh/authorized_keys

# Remove a specific SSH key
sudo nano /home/username/.ssh/authorized_keys
# Delete the line containing the key to remove

# Backup SSH keys
sudo cp -r /home/username/.ssh /backup/location/username-ssh-backup
</source>

== Troubleshooting ==

=== Common Issues ===

==== SSH Connection Refused ====

<source lang="bash">
# Check SSH service status
sudo systemctl status ssh

# Restart SSH service
sudo systemctl restart ssh

# Check SSH configuration
sudo sshd -T
</source>

==== Permission Denied ====

<source lang="bash">
# Verify file permissions
ls -la /home/username/.ssh/
# Should show: drwx------ for .ssh directory
# Should show: -rw------- for authorized_keys file

# Fix permissions if needed
sudo chmod 700 /home/username/.ssh
sudo chmod 600 /home/username/.ssh/authorized_keys
sudo chown -R username:username /home/username/.ssh
</source>

==== User Cannot Login ====

<source lang="bash">
# Check if user account is locked
sudo passwd -S username

# Check user shell
grep username /etc/passwd

# Verify home directory exists
ls -la /home/username
</source>

=== SSH Debug Mode ===

For detailed SSH connection debugging:

<source lang="bash">
# Enable verbose SSH connection
ssh -vvv username@vm-ip-address

# Check SSH server logs
sudo tail -f /var/log/auth.log
</source>

== Verification Checklist ==

After completing user setup, verify:

* [ ] User account created successfully
* [ ] Home directory exists with correct permissions
* [ ] SSH directory created with 700 permissions
* [ ] SSH public key added to authorized_keys
* [ ] authorized_keys file has 600 permissions
* [ ] User can SSH into the VM
* [ ] User has appropriate group memberships
* [ ] Shell environment is properly configured

== External Links ==

* [https://man7.org/linux/man-pages/man8/useradd.8.html useradd man page] - Linux useradd command documentation
* [https://man7.org/linux/man-pages/man1/ssh.1.html SSH man page] - SSH client documentation
* [https://man7.org/linux/man-pages/man8/sshd.8.html SSH daemon man page] - SSH server documentation
* [https://www.ssh.com/academy/ssh/authorized-key OpenSSH Authorized Keys] - SSH key authentication guide

== See Also ==

* [[Security Hardening]] - System security procedures
* [[Password Policies]] - Password policies and procedures

<!-- Categories -->
[[Category:User Management]]
[[Category:Security]]
[[Category:VM Operations]]
[[Category:Procedures]]
[[Category:SSH]]

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