# troubleshooting

You've seen this error. Everyone has. You try to push your changes and Git stops you cold: Here's your fast-track reference to diagnose and fix it. --- The...

If you've ever stared at a production alert screaming `token is not renewable` at 2 AM, you know the particular joy of Vault token management. These errors...

SSL verification errors are one of those issues that bite you at the worst possible moment — usually in production, usually when you're on-call. Here's you...

You opened your AWS bill last month and did a double-take. Data transfer charges that were $200 last quarter are now sitting at $1,800. Nothing major chang...

TechDocs is one of the most powerful features in Backstage — the idea of docs-as-code, living right next to your services in a unified developer portal, is...

If you've spent any time with Prometheus, you've seen it. That red `DOWN` label in the Targets page, accompanied by the dreaded `connection refused` error....

If you've ever stared at this error message in your logs, you know the frustration: It's one of those errors that looks simple on the surface but has about...

If you've spent any time with Terraform and AWS, you've almost certainly run into this gem at some point: It's one of those errors that looks simple but ca...

If you've ever stared at a 503 error from Nexus Repository Manager right before a critical deployment, you know the panic. Your CI/CD pipeline is blocked,...

Quick reference for debugging `no healthy upstream` errors caused by Pilot xDS push failures in multi-cluster Istio setups. --- You're running a multi-clus...

If you've spent any meaningful time with Terraform, you've probably encountered this at the worst possible moment: Everything was working fine, you added o...

Split-brain in Keepalived means both nodes think they own the VIP. Traffic gets blackholed or split unpredictably. Here's how to diagnose and fix it fast....

You've just spent an hour wrestling with Apache file permissions, carefully setting ownership to `apache:apache` and permissions to `755` on your directori...

If you've worked with ArgoCD for any meaningful amount of time, you've probably stared at that dreaded "Progressing" status, watching your application sync...

If you've worked with ArgoCD for more than five minutes, you've probably encountered this frustrating scenario: your application gets stuck in a "Progressi...

If you've been working with Helm for any length of time, you've probably encountered this frustrating error: "Error: release has no deployed revisions." It...

Getting the dreaded "Function execution took too long" error in your Cloud Functions? You're not alone. This error happens when your function exceeds the c...

If you've been working with Terraform's `for_each` argument, you've probably hit this error at least once. Don't worry – it's one of those frustrating but...

If you've been working with Helm for more than five minutes, you've probably encountered this frustrating error: "repository name already exists". It's one...

Nothing ruins your day quite like a 503 Service Unavailable error when you've spent hours configuring your shiny new Istio service mesh. I've been there mo...

You've deployed Prometheus, configured your targets, and everything looks perfect in your YAML files. Then you check the Prometheus UI and see those dreade...

Resolve Ansible become/sudo permission denied errors — fix sudoers config, passwordless sudo, and become method settings.

Resolve Ansible unreachable host failures — diagnose SSH connectivity, key auth, Python interpreter, and timeout issues.

Resolve the Apache AH00558 warning about not being able to determine the server's fully qualified domain name by setting ServerName correctly.

Diagnose and fix Apache mod_rewrite rules not being applied, covering module loading, AllowOverride settings, .htaccess issues, and rewrite logging.

Diagnose and recover AWS EC2 instances with failed system or instance status checks using stop/start, volume rescue, and auto-recovery techniques.

Systematically troubleshoot and fix AWS S3 Access Denied errors caused by IAM policies, bucket policies, ACLs, and encryption settings.

Resolve the Azure 'SubscriptionNotRegistered for resource type' error by registering the required resource provider with step-by-step instructions.

Resolve DNS lookup failures inside Docker containers — fix resolv.conf, custom networks, and upstream DNS configuration issues.

Reclaim disk space when Docker fills your drive — clean up dangling images, stopped containers, unused volumes, and build cache.

Resolve Envoy's 'upstream connect error or disconnect/reset before headers' error caused by service mesh misconfiguration, timeout issues, or unreachable backends.

Troubleshoot and fix Google Cloud Storage 403 Forbidden errors caused by missing IAM roles, service account misconfiguration, or uniform bucket-level access.

Resolve the Git error 'refusing to merge unrelated histories' when pulling or merging branches that share no common ancestor.

Resolve the GitHub Actions 'Resource not accessible by integration' error by fixing workflow permissions, GITHUB_TOKEN scopes, and repository settings.

Diagnose and resolve GitHub Actions workflows that remain stuck in 'queued' status, covering runner availability, concurrency limits, and label mismatches.

Fix Grafana dashboards that hang or take minutes to load by optimizing queries, reducing panel count, and tuning datasource settings.

Resolve the Grafana datasource error when connecting to Prometheus, caused by URL misconfiguration, network issues, or authentication problems.

Diagnose and fix HAProxy 503 Service Unavailable errors caused by backend servers failing health checks, connection limits, or misconfigured routing.

Resolve the Helm 'another operation (install/upgrade/rollback) is in progress' error caused by stuck releases with safe recovery steps.

Fix the Helm 'UPGRADE FAILED: has no deployed releases' error when a previous install failed and left the release in a broken state.

Step-by-step guide to diagnose and fix Istio sidecar proxy not being injected into Kubernetes pods, covering namespace labels, webhook configuration, and annotation overrides.

Diagnose and fix Jenkins agents that go offline mid-build — resolve network timeouts, JVM heap issues, and SSH connection drops.

Resolve Jenkins Groovy sandbox errors by approving script signatures, configuring the script security plugin, and using safe alternatives.

Clean up Kubernetes evicted pods and fix the underlying disk pressure or resource exhaustion that causes pod evictions.

Resolve ImagePullBackOff and ErrImagePull errors in Kubernetes — fix registry credentials, image tags, and network access issues.

Diagnose and fix OOMKilled errors in Kubernetes pods — understand memory limits, identify leaks, and configure resource requests correctly.

Resolve the Linux 'too many open files' error by increasing file descriptor limits at the system, user, and process level.

Diagnose and fix Nginx 502 Bad Gateway errors when proxying to upstream backends — check sockets, timeouts, and upstream health.

Resolve Nginx 'Too many open files' errors by increasing worker_rlimit_nofile, system ulimits, and kernel file descriptor limits.

Resolve Prometheus 'context deadline exceeded' errors caused by slow scrape targets, network issues, or misconfigured timeouts with this step-by-step fix guide.

Diagnose and fix Prometheus out-of-memory crashes caused by high cardinality, excessive retention, or misconfigured storage with practical steps and commands.

Diagnose and fix SSH connection refused errors after a Linux server reboot, covering sshd service, firewall rules, port configuration, and host key issues.

Resolve Terraform DynamoDB state lock errors caused by permission issues, missing tables, or misconfigured backends.

Safely unlock Terraform state when a lock is stuck after a crashed apply, CI timeout, or interrupted operation.

How to diagnose and fix HashiCorp Vault 'permission denied' errors when reading secrets, including ACL policy debugging and token inspection.

How to handle HashiCorp Vault entering sealed state after a restart, including manual unseal, auto-unseal configuration, and HA considerations.

A practical DNS troubleshooting guide for DevOps engineers — dig commands, nslookup patterns, common production failure modes, and how to diagnose each one.

Linux networking commands cheat sheet for troubleshooting — interfaces, routing, DNS lookups, connections, iptables firewalls, and tcpdump packet capture.

Configure Linux network interfaces, set up iptables/nftables/firewalld rules, troubleshoot connectivity with ss, ip, dig, and tcpdump, and secure your servers.

Diagnose Linux performance bottlenecks with top, htop, vmstat, iostat, sar, iotop, and strace — a systematic approach to finding and fixing issues.

A systematic approach to debugging CrashLoopBackOff in Kubernetes, covering the most common causes and the exact commands to diagnose each one.

Use Prometheus recording rules to pre-compute expensive queries, speed up dashboards, and make SLO calculations reliable at scale.