Vps Ubuntu

VPS Ubuntu Management Skill

This skill covers the full lifecycle of Ubuntu VPS management. Load the relevant reference file for detailed commands:

| Topic | Reference file | Load when... | |---|---|---| | Firewall & network | references/firewall.md | UFW, iptables, open ports, rate limiting | | Security hardening | references/security.md | SSH, fail2ban, kernel params, auditing, rootkits, ClamAV | | Backups | references/backups.md | rsync, Borg, rclone, cloud sync, backup testing | | Monitoring & alerts | references/monitoring.md | disk, memory, CPU, log analysis, alerting, health checks | | Cron jobs | references/cron.md | crontab syntax, scheduling, debugging, systemd timers | | Web server | references/webserver.md | Nginx, SSL, PM2, reverse proxy, compression, rate limiting | | Containers | references/containers.md | Docker, Docker Compose, networking, image cleanup |

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Server Provisioning — Fresh Ubuntu VPS

Run these steps immediately after first SSH login to a new server:

# 1. Update system
apt update && apt upgrade -y

# 2. Set hostname and timezone
hostnamectl set-hostname myserver
timedatectl set-timezone UTC   # or your preferred timezone

# 3. Create deploy user (never run apps as root)
adduser deploy
usermod -aG sudo deploy

# 4. Copy SSH key to deploy user
mkdir -p /home/deploy/.ssh
cp /root/.ssh/authorized_keys /home/deploy/.ssh/
chown -R deploy:deploy /home/deploy/.ssh
chmod 700 /home/deploy/.ssh && chmod 600 /home/deploy/.ssh/authorized_keys

# 5. Firewall — allow SSH before enabling
ufw default deny incoming && ufw default allow outgoing
ufw allow 22/tcp
ufw allow 80/tcp
ufw allow 443/tcp
ufw enable

# 6. Harden SSH (see references/security.md for full config)
sed -i 's/#PermitRootLogin yes/PermitRootLogin no/' /etc/ssh/sshd_config
sed -i 's/#PasswordAuthentication yes/PasswordAuthentication no/' /etc/ssh/sshd_config
sshd -t && systemctl reload ssh

# 7. Install essentials
apt install -y curl wget git unzip htop tmux fail2ban ufw \
  certbot python3-certbot-nginx logwatch unattended-upgrades

# 8. Enable automatic security updates
dpkg-reconfigure --priority=low unattended-upgrades

# 9. Set up fail2ban
cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local
systemctl enable --now fail2ban

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Quick Diagnostics — Run These First

When a user reports a server problem, start with:

# System overview
uptime && free -h && df -h

# Top processes
ps aux --sort=-%cpu | head -15

# Network connections
ss -tulpn

# Recent errors
journalctl -p err -n 50 --no-pager

# Failed systemd services
systemctl --failed

# Last logins and failed SSH attempts
last -n 20
grep "Failed password" /var/log/auth.log | tail -20

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Server Health Scorecard

Before doing anything else on a VPS, run this mental checklist:

• [ ] Disk: df -h — any partition >80% full?
• [ ] Memory: free -h — swap in use? High?
• [ ] Load: uptime — load average > number of CPUs?
• [ ] Firewall: ufw status — active and rules correct?
• [ ] Updates: apt list --upgradable 2>/dev/null | wc -l — security updates pending?
• [ ] Failed services: systemctl --failed — anything crashed?
• [ ] Auth log: grep "Failed password" /var/log/auth.log | wc -l — brute force?
• [ ] Backups: last backup timestamp — recent and verified?
• [ ] SSL certs: certbot certificates — expiry within 30 days?
• [ ] Docker: docker system df — disk consumed by images/volumes?
• [ ] Tailscale: tailscale status — connected to mesh?

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Emergency Procedures

Server is unreachable / SSH locked out

1. Use VPS provider's web console (DigitalOcean, Hetzner, Vultr all have one)
2. Check if UFW blocked your IP: ufw status then ufw allow from YOUR_IP
3. fail2ban may have banned you: fail2ban-client status sshd then fail2ban-client set sshd unbanip YOUR_IP
4. Check SSH service: systemctl status ssh

Disk 100% full — server broken

# Find what's eating space
du -sh /* 2>/dev/null | sort -rh | head -20
du -sh /var/log/* | sort -rh | head -10

# Emergency cleanup
journalctl --vacuum-size=100M        # trim systemd logs
apt clean                            # clear apt cache
docker system prune -f 2>/dev/null   # clear Docker if installed
find /tmp -mtime +7 -delete          # old temp files

# Rotate logs immediately
logrotate -f /etc/logrotate.conf

Server under attack / high load

# See what's hammering the server
netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -rn | head -20

# Block an IP immediately
ufw deny from ATTACKER_IP

# Find CPU-hungry processes
ps aux --sort=-%cpu | head -10

# Kill runaway process
kill -9 PID

Memory exhausted / OOM killer

# Check OOM kill history
dmesg | grep -i "killed process"
grep -i "out of memory" /var/log/syslog | tail -20

# See what's using RAM
ps aux --sort=-%mem | head -15
free -h

# Add emergency swap (if none exists)
fallocate -l 2G /swapfile
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile

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Safety Rules — Always Follow

Before running any destructive command, state it and ask for confirmation:

• rm -rf anything — STOP, confirm path and scope
• ufw reset — will drop ALL firewall rules
• iptables -F — flushes all rules, server becomes open
• Editing /etc/ssh/sshd_config — test before reload or you risk lockout
• reboot / shutdown — confirm timing with user
• Dropping a database — always confirm and verify backup exists first
• docker system prune -a — removes all unused images, not just dangling

Always test SSH config before restarting:

sshd -t   # test config validity — ALWAYS run before: systemctl restart ssh

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Tailscale VPN Setup & SSH Connection

Install Tailscale

curl -fsSL https://tailscale.com/install.sh | sh
tailscale up --ssh          # enable Tailscale SSH (optional)
tailscale status            # verify connection
tailscale ip -4             # get Tailscale IPv4 address

Keep-Alive Configuration (prevents drop after inactivity)

Local ~/.ssh/config — prevents client-side timeout:

Host vps-tailscale
    HostName 100.x.x.x
    User youruser
    ServerAliveInterval 60
    ServerAliveCountMax 10
    TCPKeepAlive yes
    ConnectTimeout 30

VPS /etc/ssh/sshd_config — prevents server-side timeout:

ClientAliveInterval 120
ClientAliveCountMax 10
TCPKeepAlive yes

Always run sshd -t && systemctl reload ssh after editing.

Why it drops: VPS providers (Hetzner, DO, Vultr) NAT-timeout idle UDP connections in 60-90 seconds, which silently kills the WireGuard tunnel Tailscale uses. ServerAliveInterval 60 keeps SSH traffic flowing through the tunnel, preventing the drop.

Reconnect Command (if session drops anyway)

tailscale status           # verify tunnel is up
ssh vps-tailscale          # reconnect using config alias

WireGuard (manual alternative to Tailscale)

apt install wireguard -y

# Generate keys
wg genkey | tee /etc/wireguard/private.key | wg pubkey > /etc/wireguard/public.key
chmod 600 /etc/wireguard/private.key

# Config: /etc/wireguard/wg0.conf
[Interface]
PrivateKey = 
Address = 10.0.0.1/24
ListenPort = 51820

[Peer]
PublicKey = 
AllowedIPs = 10.0.0.2/32

# Enable
systemctl enable --now wg-quick@wg0
ufw allow 51820/udp

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Unattended Upgrades

apt install unattended-upgrades -y
dpkg-reconfigure --priority=low unattended-upgrades

# Verify enabled
cat /etc/apt/apt.conf.d/20auto-upgrades
# Should show:
# APT::Periodic::Update-Package-Lists "1";
# APT::Periodic::Unattended-Upgrade "1";

# Check what will be upgraded
unattended-upgrades --dry-run --debug

# View upgrade log
cat /var/log/unattended-upgrades/unattended-upgrades.log

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Log Rotation Quick Reference

# Check existing configs
ls /etc/logrotate.d/

# Test config (dry run)
logrotate -d /etc/logrotate.d/myapp

# Force immediate rotation
logrotate -f /etc/logrotate.conf

# Example: /etc/logrotate.d/myapp
/var/log/myapp/*.log {
    daily
    rotate 14
    compress
    delaycompress
    missingok
    notifempty
    create 0640 www-data www-data
    postrotate
        systemctl reload myapp > /dev/null 2>&1 || true
    endscript
}

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: arturseo-geo
• Source: arturseo-geo/claude-code-skills
• License: MIT
• Homepage: https://thegeolab.net

Install and usage instructions live in the source repository linked above.