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I Just Saved Our Company By Unplugging And Plugging It In Again

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By Usman Masood Ashraf
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I Just Saved Our Company By Unplugging And Plugging It In Again

I Just Saved Our Company By Unplugging And Plugging It In Again: The Untold Power of Hardware Diagnostics in DevOps

INTRODUCTION

The alert came at the worst possible moment - during a medical appointment, with a critical Lenovo server reporting a “Pwr Rail D” error after a scheduled reboot. IPMI remote management failed. Colleagues escalated. Then came the 3am realization: sometimes the oldest trick in the book (“turn it off and on again”) remains the most powerful weapon in a DevOps engineer’s arsenal.

This isn’t just another war story - it’s a masterclass in why infrastructure resilience demands equal mastery of hardware diagnostics and software automation. In an era dominated by Kubernetes clusters and Infrastructure-as-Code, we’ve developed dangerous blind spots to the physical layer that underpins everything.

In this comprehensive guide, we’ll examine:

  • The critical role of hardware monitoring in modern DevOps
  • Advanced IPMI/BMC management techniques
  • Integrating physical layer monitoring into Zabbix/Prometheus
  • Automated recovery workflows for hardware faults
  • When and how to perform “cold reboots” safely
  • Building resilient infrastructure that survives hardware failures

Whether you’re managing a homelab rack or enterprise data center, understanding these hardware interaction patterns separates competent engineers from infrastructure heroes.

UNDERSTANDING THE TOPIC

What is Hardware Diagnostics in DevOps?

While DevOps typically focuses on software automation, hardware diagnostics involves monitoring and managing physical server components:

  1. Baseboard Management Controllers (BMC): Dedicated microcontrollers providing out-of-band management via IPMI or Redfish API
  2. Intelligent Platform Management Interface (IPMI): Standard protocol for monitoring hardware sensors (temperature, voltage, fans)
  3. Power Distribution Units (PDUs): Smart power strips enabling per-outlet control
  4. Serial over LAN (SOL): Console access independent of OS status

Why Hardware Matters in Cloud-Native Environments

Consider these real-world scenarios:

Failure ModeSoftware FixHardware Fix
RAM stick failureMemory error detectionPhysical replacement
PSU capacitor degradationVoltage monitoringCold reboot cycle
RAID controller lockupNonePower cycle

The 2023 Uptime Institute report found 78% of data center outages involved hardware or power issues - most preventable through proper monitoring.

Evolution of Hardware Management

  1. 1998: IPMI v1.0 introduced by Intel
  2. 2004: IPMI v2.0 added encryption and SOL
  3. 2015: Redfish RESTful API standard launched
  4. 2020: OpenBMC project gains enterprise adoption

Modern implementations like Lenovo XClarity Controller (XCC) combine legacy IPMI with Redfish API endpoints for JSON-based management.

Key Capabilities of Modern BMCs

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# Example IPMI commands
ipmitool -H 192.168.1.100 -U admin -P password chassis power status
ipmitool -H 192.168.1.100 sensor list
ipmitool -H 192.168.1.100 sol activate

Critical features include:

  • Remote power control (soft/hard reset, power cycle)
  • Sensor monitoring (voltage, temperature, fan speed)
  • Hardware inventory (DIMM slots, PCIe devices)
  • Alerting thresholds configurable via SDR (Sensor Data Repository)

The “Power Cycle” Controversy

While considered a last resort, controlled power cycling resolves certain hardware states unreachable via software:

  1. PSU Rail Synchronization Issues: Where redundant power supplies lose phase alignment
  2. PCIe Bus Hangs: Stubborn device lockups requiring full power discharge
  3. BMC Firmware Glitches: Microcontroller crashes needing cold restart

As demonstrated in the opening scenario, Lenovo’s “Pwr Rail D” error specifically indicates DC power rail instability often resolved by complete power drainage.

PREREQUISITES

Hardware Requirements

  1. Server Platform: BMC/IPMI support (Dell iDRAC, HPE iLO, Lenovo XCC)
  2. Network Connectivity: Dedicated management port or shared LAN
  3. Power Infrastructure: Smart PDU with per-outlet control (APC, CyberPower)
  4. Console Access: Serial port or SOL capability

Software Dependencies

ComponentMinimum VersionPurpose
ipmitool1.8.18CLI BMC management
FreeIPMI1.6.9Alternative IPMI stack
Redfish PowerShell2.0Microsoft Redfish module
Zabbix Server5.0 LTSMonitoring integration

Security Considerations

  1. Management Network Isolation: BMC interfaces should reside on dedicated VLAN
  2. Credential Rotation: BMC passwords changed quarterly (PCI-DSS 8.2.4)
  3. Certificate Management: Install valid TLS certificates for HTTPS interfaces
  4. Access Logging: Audit all IPMI sessions via syslog forwarding

Pre-Installation Checklist

  1. Verify BMC firmware version against vendor advisories
  2. Confirm physical console access as fallback
  3. Document PDU outlet mappings
  4. Establish maintenance windows for power operations
  5. Test UPS runtime under full load

INSTALLATION & SETUP

Configuring IPMI Access

First, enable IPMI over LAN in BIOS/BMC settings, then configure network access:

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# Set static IP on BMC
ipmitool -I lanplus -H 192.168.1.100 -U admin -P password lan set 1 ipsrc static
ipmitool -I lanplus -H 192.168.1.100 -U admin -P password lan set 1 ipaddr 192.168.1.100
ipmitool -I lanplus -H 192.168.1.100 -U admin -P password lan set 1 netmask 255.255.255.0

Integrating with Zabbix

Create a template for hardware monitoring in /etc/zabbix/zabbix_agentd.d/ipmi.conf:

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UserParameter=ipmi.powerstatus,ipmitool -I lanplus -H 192.168.1.100 -U $IPMI_USER -P $IPMI_PASSWORD chassis power status | grep -c "on"
UserParameter=ipmi.temp[*],ipmitool -I lanplus -H 192.168.1.100 -U $IPMI_USER -P $IPMI_PASSWORD sensor reading "$1" | awk '/Sensor Reading/ {print $4}'

Use macros for credentials stored in Zabbix vault:

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{$IPMI_USER} = "monitoring_user"
{$IPMI_PASSWORD} = "secure_password"

Automated Recovery Workflows

Create an Ansible playbook for controlled power cycling:

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- name: Recover from hardware hang
  hosts: problematic_servers
  vars:
    bmc_ip: ""
    bmc_user: "admin"
    bmc_pass: "!vault_encrypted_password"
    
  tasks:
    - name: Attempt soft reboot
      community.general.ipmi:
        name: ""
        user: ""
        password: ""
        state: reboot

    - name: Wait for response
      wait_for_connection:
        timeout: 300
        
    - name: Force power cycle if still down
      community.general.ipmi:
        name: ""
        user: ""
        password: ""
        state: cycle
      when: ansible_connection == 'failed'

Verification Steps

  1. Confirm IPMI sensor access:
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    ipmitool -H 192.168.1.100 sensor list | grep "PSU"
PSU1 Status      | 0x0        | ok
PSU2 Status      | 0x0        | ok
  2. Test power commands:
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    ipmitool -H 192.168.1.100 chassis power cycle
  3. Validate Zabbix integration:
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    zabbix_get -s 127.0.0.1 -k "ipmi.temp[CPU1 Temp]"
42

CONFIGURATION & OPTIMIZATION

BMC Security Hardening

  1. Disable Default Accounts:
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    ipmitool -H 192.168.1.100 user set name 1 "disabled_user"
ipmitool -H 192.168.1.100 user set password 1 "$RANDOM_STRING"
  2. Configure Session Timeouts:
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    ipmitool -H 192.168.1.100 lan set 1 auth ADMIN MD5
ipmitool -H 192.168.1.100 lan set 1 session_timeout 600
  3. Enable TLS 1.2+:
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    ipmitool -H 192.168.1.100 lan set 1 cipher_privs aaaaaaaaaaaaaaa

Performance Tuning

  1. Sensor Polling Intervals:
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    # In /etc/sysconfig/ipmi
DAEMON_ARGS="-c -O /var/log/ipmi.log -I 30"
  2. Zabbix Low-Level Discovery:
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    {
    "data": [
        {
            "{#SENSOR_NAME}": "CPU1 Temp",
            "{#SENSOR_UNIT}": "C"
        }
    ]
}
  3. PDU Sequencing:
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    # APC PDU startup sequence
outlet 1 delay=60  # Storage
outlet 2 delay=120 # Compute
outlet 3 delay=180 # Networking

Alert Threshold Best Practices

Sensor TypeWarningCriticalRecovery
CPU Temp70°C85°C65°C
PSU Input200V190V205V
Fan Speed30%20%40%

USAGE & OPERATIONS

Daily Monitoring Tasks

  1. Review BMC error logs:
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    ipmitool -H 192.168.1.100 sel list
  2. Verify sensor thresholds:
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    ipmitool -H 192.168.1.100 sensor thresh "CPU1 Temp" upper 85 80
  3. Check PSU redundancy:
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    ipmitool -H 192.168.1.100 dcmi power reading

Maintenance Procedures

Controlled Power Cycle Protocol:

  1. Drain workloads via orchestration:
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    kubectl drain node01 --ignore-daemonsets
  2. Initiate graceful shutdown:
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    ipmitool -H 192.168.1.100 chassis power soft

  3. Wait 60 seconds for capacitors to discharge

  4. Cut power via PDU:
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    apcupsd -e -k1 -m admin -p password
  5. Restore power after 30 seconds:
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    apcupsd -e -o1 -m admin -p password

Backup Strategies

  1. BMC Configuration Backup:
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    ipmitool -H 192.168.1.100 bmc backup filename=bmc_config.bin
  2. PDU Outlet Mapping:
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    # Rack A PDU Layout
outlet1: racka-node01 (192.168.1.101)
outlet2: racka-node02 (192.168.1.102)

TROUBLESHOOTING

Common Hardware Errors

Pwr Rail D Error (Lenovo Specific):

  1. Check PSU status:
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    ipmitool -H 192.168.1.100 dcmi power get_limit
  2. Verify voltage stability:
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    ipmitool -H 192.168.1.100 sensor reading "PSU1 Vout"
  3. Force PSU failover:
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    ipmitool -H 192.168.1.100 raw 0x3a 0x11 0x01 0x00

Recovery Procedure:

graph TD
    A[Alert: Pwr Rail D] --> B{Drain Node}
    B --> C[Soft Shutdown]
    C --> D[PDU Power Off]
    D --> E[Wait 60s]
    E --> F[PDU Power On]
    F --> G[Verify Boot]

Debug Commands

  1. Check SEL timestamps:
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    ipmitool -H 192.168.1.100 sel time get
  2. Monitor real-time sensors:
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    watch -n 5 'ipmitool -H 192.168.1.100 sensor reading "PSU1 Vout"'
  3. Force BMC reset:
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    ipmitool -H 192.168.1.100 mc reset cold

CONCLUSION

The “plug it back in” solution that saved our company wasn’t luck - it was the culmination of proper hardware monitoring, documented recovery procedures, and understanding when software-based solutions reach their limits. In DevOps, we must remember that even the most advanced Kubernetes cluster ultimately depends on physical hardware behaving predictably.

Key takeaways:

  1. Monitor the Metal: Integrate IPMI/Redfish into your observability stack
  2. Automate Recovery: Build playbooks for common hardware failure modes
  3. Document Everything: PDU mappings, BMC credentials, power sequences
  4. Test Failure Scenarios: Practice cold reboots during maintenance windows

To dive deeper into hardware automation:

Remember: The most elegant Terraform configuration won’t save you from a failing power supply. Master both layers of the stack - and you’ll become the engineer who saves the company at 3am.

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This post is licensed under CC BY 4.0 by the author.