BookStack on GKE Autopilot

BookStack is a free, open-source, MIT-licensed wiki and documentation platform built on Laravel (PHP), organising content as Shelves → Books → Chapters → Pages with WYSIWYG and Markdown editing, full-text search, page revisions, and granular permissions. This module deploys BookStack on GKE Autopilot on top of the App_GKE foundation, which provisions and manages the shared Google Cloud and Kubernetes infrastructure.

This guide focuses on the cloud services BookStack uses and how to explore and operate them from the Google Cloud Console and the command line. For the mechanics that are common to every GKE application — Workload Identity, ingress, autoscaling, CI/CD, Cloud Armor, IAP, Binary Authorization, VPC Service Controls, backups, and the deployment lifecycle — refer to the App_GKE foundation guide rather than repeating them here.

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What BookStack costs on RAD, and how that compares

BookStack on RAD's GKE Autopilot module costs about US$110 a month in your own Google Cloud project, with no extra licence fee — BookStack is open source. In a project RAD manages for you, the same deployment is metered at 99 credits a day (about 2,970 a month, about US$297 at the top-up price). Or see the Cloud Run guide for the lower-cost option. If you only need BookStack occasionally — studying, a demo, a short-lived project — a RAD-managed project can be deleted and restored within 30 days for a few credits, so that monthly figure becomes a few dollars instead. See Pause it for free, below.

What you pay on RAD

BookStack is open source, so there is no licence fee. You pay for three things:

	In a Google Cloud project you own	In a project RAD manages for you
Module fee, once per deployment	110 credits (US$11 at the top-up price)	99 credits (10% lower)
Build time	A few credits per build (roughly 3–6 credits)	The same
Google Cloud running cost	Billed by Google to your own billing account, about US$110 a month for the default configuration (table below)	Metered hourly in credits; RAD publishes 99 credits a day, about 2,970 a month (about US$297 at the top-up price)
Who owns what	You own the project and its billing; RAD deploys and updates it	RAD owns the project, with guardrails, quotas and budget alerts; you get console access, and a minimum purchased balance is held in reserve

10 credits cost US$1 on a one-off top-up, and less on a monthly plan. In a project RAD manages, the database, file server and network are shared by every application in the project, so a second application does not add a second database.

Default running cost in your own project (us-central1, Google list prices):

Resource (module default)	Per month
GKE Autopilot pod, 1x vCPU / 2 GiB	US$39.68
Cloud SQL for MySQL, 1 vCPU / 3.75 GB, zonal, 10 GB SSD	US$51.02
NFS/cache file server (small VM)	US$13.43
Cloud NAT and networking	US$5
Cloud Storage (add-ons, backups)	US$1
GKE cluster management fee	shared across every GKE app in the project; $0 if this is your only cluster, else ~73
Total (excluding the shared GKE cluster fee)	about US$110

Cloud SQL and Cloud Run/GKE pod pricing is the same in africa-south1 (Johannesburg); the small VM costs about 10% more there.

• GKE Autopilot does not scale to zero. At least one pod always runs, so the cost above applies whether or not anyone is using the app; extra pods are added only under load.

How it compares, for a small team's wiki

BookStack's own project does not sell hosting; a handful of third-party providers list BookStack hosting on bookstackapp.com's sponsor page, but RAD has not fetched a current price from any of them, so none is quoted here. The comparison that can be verified is a bare server:

• A Hetzner CPX22 or DigitalOcean droplet (2 vCPU/4 GB, about US$24/month) or a GCP e2-standard-2 (2 vCPU/8 GB, about US$49/month) would run BookStack and its MySQL database.
• On a bare VPS you run MySQL, backups, security patches and upgrades yourself. RAD's module gives you managed Cloud SQL, Secret Manager and Cloud Monitoring for the module fee plus the Google Cloud usage above.

Pause it for free: delete a RAD-managed project, restore it when you need it

If BookStack runs in a project RAD manages for you, deleting the whole project — rather than deleting just this module — unlinks its billing first, then asks Google to delete the project outright. Google keeps it, recoverable, for 30 days, and because billing is already unlinked, nothing is charged while it waits. Unlike deleting one module, this does not tear down Cloud SQL, any VM or the compute resource one by one: the whole project simply stops.

• Restoring is a check, not a rebuild. Within 30 days, the project's owner can ask Google to undelete the project and reattach its billing account, then run Update on each deployment to confirm everything came back. Because nothing was individually destroyed, that Update finds the same resources already there, and an Update never charges the module fee again. For a typical 2–3-deployment chain this costs only a handful of credits in total (roughly 5–10 credits, under US$1).
• What this needs. You must own the project (not one RAD only manages billing for), restore it yourself within 30 days — after that Google deletes it for good — and clear the tier's admission floor again (100 credits for the sandbox tier most study/demo use fits). Google says most services are fully working again within 36 hours of a restore.
• One real gap: nightly backups do not survive. Backups are written to a bucket inside the project, and that bucket has Cloud Storage's soft-delete turned off, so it is very likely gone as soon as the project is deleted — even though the project itself is recoverable for 30 days. Copy a backup out (to Google Drive, or a bucket outside the project) before deleting if there is anything in it worth keeping; for a default install with nothing irreplaceable, this does not matter.

Source: Delete and restore projects.

Pay only while you use it, the other way: delete and redeploy

In your own project, or once the 30-day restore window above has passed, the way to stop paying is to delete the deployment and deploy it again when you need it.

• What a redeploy costs. The module fee again, plus the builds: about 114 credits (about US$11.40) at the top-up price, and roughly 15–20 minutes of build time (RAD's own platform average). Deleting saves money only once BookStack would otherwise sit unused for about 2 days or more — in your own project that is about US$3.67 a day, and in a RAD-managed one it is 99 credits a day.
• Most of the running cost here is usually the database and/or the shared file/cache VM or cluster. They stop only when nothing else in the project uses them, so deleting BookStack while another application shares the project saves only BookStack's own compute part.
• Keep data first. Nightly backups go to a bucket inside the deployment and are deleted with it, so copy the latest backup out before deleting if you want to keep it.

Lab sessions and Managed Environments

• Lab sessions, for training. A trainer runs a session for a class. Each participant gets the app in their own Google Cloud project for 15 minutes to 24 hours, within an allowance the trainer sets. Either the trainer funds every place, or each participant pays for their own. Everything is deleted when the session ends and unused credits go back to the trainer.
• Managed Environments, for consultancies. A partner runs the app for a client from a ring-fenced wallet it funds, and settles with the client directly. If the wallet runs low, billing pauses and the data is kept, so nobody receives an unexpected charge. At the end the partner hands the project over and the deployments become the client's own.

Credits can be bought in more than 20 currencies, including XAF, XOF, NGN, GHS, KES and ZAR, by card, bank transfer or mobile money.

Sources (8 October 2026): Google Cloud list prices from the Cloud Billing Catalog API; RAD fees and the daily-credit estimate from radmodules.dev/pricing; Delete and restore projects for the pause/restore window and backup-bucket caveat; prices change, check each source before relying on a figure.

1. Overview

BookStack runs as a PHP web workload on GKE Autopilot. The deployment wires together a focused set of Google Cloud services:

Capability	Google Cloud service	Notes
Compute	GKE Autopilot	PHP (LinuxServer) pods, 1 vCPU / 2 GiB by default, single replica (NFS-backed)
Database	Cloud SQL for MySQL 8.0	Required — BookStack does not support PostgreSQL or other engines
Object storage	Cloud Storage	A dedicated data bucket (gcs-bookstack<tenant>-data) provisioned automatically
Persistent files	Filestore / NFS	Uploaded images and attachments persisted at /var/lib/bookstack
Cache & sessions	Redis (optional)	Disabled by default; BookStack uses the local cache/session driver
Secrets	Secret Manager	Auto-generated Laravel APP_KEY; database password
Ingress	Cloud Load Balancing	External LoadBalancer, custom domain + managed certificate + static IP by default

Sensible defaults worth knowing up front:

• MySQL 8.0 is mandatory. The database engine is fixed by the shared application layer (database_type = "MYSQL_8_0"); PostgreSQL is not supported and selecting another engine breaks startup.
• The prebuilt linuxserver/bookstack image is used directly. There is no custom Cloud Build; the official LinuxServer.io image is mirrored into Artifact Registry (enable_image_mirroring = true) and deployed as-is.
• The container listens on port 80 (container_port = 80, container_protocol = "http1").
• NFS persistence of uploads is on by default. enable_nfs = true mounts NFS at /var/lib/bookstack so uploaded images and attachments survive restarts, redeploys, and pod rescheduling. Because BookStack is NFS-backed, the Deployment uses the Recreate update strategy (a single pod against the shared volume).
• A single replica is maintained (min_instance_count = 1, max_instance_count = 1; GKE has no scale-to-zero). Do not scale beyond one pod without external session/cache coordination — multiple pods against the same NFS volume and DB deadlock.
• APP_KEY is immutable after first boot. The Laravel app key is generated once and stored in Secret Manager; rotating it makes all encrypted DB values undecryptable.
• The image runs php artisan migrate --force automatically on start, so the schema is created on first boot after db-init provisions the database and user — there is no separate migration job.
• A default administrator is seeded by the LinuxServer image: admin@admin.com with password password. Change it immediately on first login.
• GKE connects to Cloud SQL through the Auth Proxy sidecar on 127.0.0.1:3306 (enable_cloudsql_volume = true), and the GKE wiring overrides DB_HOST = "127.0.0.1".
• A custom domain, managed certificate, and reserved static IP are enabled by default (enable_custom_domain = true, reserve_static_ip = true), with session_affinity = "ClientIP" for sticky UI sessions.

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2. Google Cloud Services & How to Explore Them

All commands assume you have run gcloud container clusters get-credentials <cluster> --region <region> --project <project> and that PROJECT, REGION, and NAMESPACE are set. The namespace and other identifiers are reported in the deployment Outputs.

A. GKE Autopilot — the BookStack workload

BookStack pods are scheduled on Autopilot, which bills for the CPU/memory the pods actually request. Because the app is NFS-backed, the workload runs as a single-replica Deployment using the Recreate strategy.

• Console: Kubernetes Engine → Workloads → select the BookStack workload to see pods, revisions, and events. Kubernetes Engine → Services & Ingress shows the external IP.
• CLI:

  kubectl get pods,svc -n "$NAMESPACE"
  kubectl logs -n "$NAMESPACE" deploy/<service-name> --tail=100
  kubectl describe deploy/<service-name> -n "$NAMESPACE"    # strategy, events

See App_GKE for how Autopilot, scaling, and the workload type (Deployment vs StatefulSet) are managed.

B. Cloud SQL for MySQL 8.0

BookStack stores all application data (books, pages, users, revisions, permissions) in a managed Cloud SQL for MySQL 8.0 instance. Pods reach it privately through the Cloud SQL Auth Proxy sidecar on 127.0.0.1:3306 (enable_cloudsql_volume = true); no public IP is exposed. On first deploy an initialization Job creates the application database and user.

• Console: SQL → select the instance for connections, backups, flags, and metrics.
• CLI:

  gcloud sql instances list --project "$PROJECT"
  gcloud sql instances describe <instance-name> --project "$PROJECT"
  # Open an interactive shell to inspect schema/data:
  gcloud sql connect <instance-name> --user=bookstack --database=<db-name> --project "$PROJECT"

The instance name, database name, user, and the Secret Manager secret holding the password are all surfaced in the Outputs. For the connection model, automated backups, and password rotation, see App_GKE.

C. Cloud Storage

A dedicated Cloud Storage bucket (storage_buckets default: name_suffix = "data", resulting in gcs-bookstack<tenant>-data) is provisioned automatically. The workload service account is granted access. Additional buckets can be declared via storage_buckets.

• Console: Cloud Storage → Buckets.
• CLI:

  gcloud storage buckets list --project "$PROJECT"
  gcloud storage ls gs://<uploads-bucket>/        # bucket name is in the Outputs

See App_GKE for CMEK options and GCS Fuse mounts.

D. Redis (optional cache & sessions)

Redis is disabled by default (enable_redis = false); BookStack uses its local cache and session drivers. When enable_redis = true is set, the shared layer injects REDIS_HOST and REDIS_PORT. When redis_host is left empty and enable_nfs is true, the NFS server VM's co-hosted Redis IP is used.

• Console: Memorystore → Redis (if using a managed instance).
• CLI:

  redis-cli -h <redis-host> ping
  redis-cli -h <redis-host> info keyspace
  # Confirm the DB wiring injected into the running pod:
  kubectl exec -n "$NAMESPACE" deploy/<service-name> -- env | grep -E 'DB_|REDIS_'

E. Secret Manager

One cryptographic secret is generated automatically and stored in Secret Manager: the Laravel APP_KEY (base64:<44-char base64>), used to encrypt all application data that BookStack stores encrypted. The database password is managed separately by the foundation.

• Console: Security → Secret Manager.
• CLI:

  gcloud secrets list --project "$PROJECT"
  gcloud secrets versions access latest --secret=<secret-name> --project "$PROJECT"

The database password secret name is in the Outputs. See App_GKE for the Secret Store CSI integration and rotation.

F. Networking & ingress

By default the workload is exposed through an external Cloud Load Balancing IP with a custom domain and Google-managed certificate (enable_custom_domain = true), and a static IP is reserved (reserve_static_ip = true) so the address survives redeploys.

• Console: Network services → Load balancing; VPC network → IP addresses.
• CLI:

  kubectl get ingress,svc -n "$NAMESPACE"
  gcloud compute addresses list --project "$PROJECT"

See App_GKE for custom domains, Cloud CDN, and static IP details.

G. Cloud Logging & Monitoring

Pod stdout/stderr flow to Cloud Logging; GKE and Cloud SQL metrics flow to Cloud Monitoring. Optional uptime checks and alert policies are available.

• Console: Logging → Logs Explorer; Monitoring → Dashboards / Alerting.
• CLI:

  gcloud logging read 'resource.type="k8s_container" AND resource.labels.namespace_name="'"$NAMESPACE"'"' \
    --project "$PROJECT" --limit 50

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3. BookStack Application Behaviour

• First-deploy database setup. An initialization Job runs db-init.sh using mysql:8.0-debian. It detects the Cloud SQL socket or TCP endpoint, waits for MySQL to be reachable, creates the application database and user, grants privileges, verifies the app user can connect, and gracefully shuts down the Cloud SQL Auth Proxy sidecar. The job is idempotent and safe to re-run (max_retries = 3).
• Schema auto-migration on start. The LinuxServer BookStack image runs php artisan migrate --force automatically on every container start, so the schema is created on first boot and upgraded on later boots — there is no separate migration job.
• APP_KEY is immutable after first boot. The Laravel app key is generated once and written to Secret Manager. Rotating it makes all encrypted DB values (two-factor secrets, some settings) permanently undecryptable. Only rotate during a planned maintenance window with a re-encryption plan.
• First-run administrator. The image seeds a default admin account, admin@admin.com / password. Change the password (and ideally the email) immediately after the first login.
• Uploaded files live on NFS. Images, attachments, and other uploads are stored on the filesystem under /var/lib/bookstack, which is NFS-backed by default. The Deployment therefore uses the Recreate strategy so only one pod ever writes to the shared volume — do not scale to multiple replicas without external coordination.
• Health path. The liveness probe targets /status by default — BookStack's unauthenticated JSON health endpoint that reports app/database/cache/session status. The startup probe is a TCP check. Allow a generous first-boot window (300-second initial delay) for the automatic migrations.
• Inspect job execution:

  kubectl get jobs -n "$NAMESPACE"
  kubectl logs -n "$NAMESPACE" job/<job-name>

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4. Configuration Variables

Variables are grouped exactly as they appear on the deployment platform. Only settings specific to or notable for BookStack are listed; every other input is inherited from App_GKE with its standard behaviour and defaults.

Group 1 — Project & Identity

Variable	Default	Description
project_id	(required)	Target Google Cloud project.
region	us-central1	Region for the workload and regional resources.

Group 2 — Deployment Environment

Variable	Default	Description
tenant_id	demo	Short suffix that makes resource names unique per environment.
support_users	[]	Emails granted project access and monitoring alerts.
resource_labels	{}	Labels applied to all resources for cost/ownership tracking.

Group 3 — Application Identity

Variable	Default	Description
application_name	bookstack	Base name for resources. Do not change after first deploy.
application_display_name	BookStack	Human-readable name shown in the Console.
application_description	BookStack wiki on GKE Autopilot	Workload description.
application_version	latest	linuxserver/bookstack image tag; pin (e.g. version-v24.10) in production.

Group 4 — Runtime & Scaling

Variable	Default	Description
deploy_application	true	Set false to provision infrastructure only.
container_image_source	prebuilt	Deploy the mirrored LinuxServer image directly — no custom build.
container_image	""	Override image reference; leave empty to use the mirrored default.
enable_image_mirroring	true	Mirror the LinuxServer image into Artifact Registry before deployment.
min_instance_count	1	Minimum replicas; keep at 1 (NFS-backed single pod).
max_instance_count	1	Maximum replicas. Do not raise without external session/cache coordination.
container_port	80	BookStack listens on port 80.
container_protocol	http1	HTTP/1.1.
cpu_limit	1000m	CPU per pod; 1 vCPU by default.
memory_limit	2Gi	Memory per pod.
timeout_seconds	300	Maximum request duration (0–3600 seconds).
enable_cloudsql_volume	true	Cloud SQL Auth Proxy sidecar (127.0.0.1:3306); required on GKE.

Group 5 — Environment Variables & Secrets

Variable	Default	Description
environment_variables	{}	Extra non-secret settings (e.g. APP_URL, mail config). Do not set APP_KEY or DB_* here.
secret_environment_variables	{}	Map of env var → Secret Manager secret name.
secret_propagation_delay	30	Seconds to wait after secret creation before proceeding.
secret_rotation_period	2592000s	Secret Manager rotation notification frequency.

Group 6 — GKE Backend & Cluster

Variable	Default	Description
service_type	LoadBalancer	How the Kubernetes Service is exposed.
workload_type	null	Resolves to Deployment (default) unless a StatefulSet is requested.
session_affinity	ClientIP	Sticky routing keeps a client's UI session on one pod.
enable_network_segmentation	false	Create Kubernetes NetworkPolicy resources.
termination_grace_period_seconds	30	Seconds to wait after SIGTERM before SIGKILL.

Group 7 — StatefulSet

Variable	Default	Description
stateful_pvc_enabled	null	Leave off — BookStack uses NFS, not per-pod PVCs.
stateful_pvc_size	10Gi	Per-pod PVC storage size (if enabled).
stateful_pvc_mount_path	/data	Container mount path for the PVC.
stateful_pvc_storage_class	standard-rwo	Kubernetes StorageClass for PVCs.

Group 8 — Resource Quota

Variable	Default	Description
enable_resource_quota	false	Enforce a namespace ResourceQuota.
quota_cpu_requests / quota_cpu_limits	""	CPU quota.
quota_memory_requests / quota_memory_limits	""	Memory quota — use binary units (4Gi, 8192Mi).
quota_max_pods / quota_max_services / quota_max_pvcs	""	Object-count quotas.

Group 9 — Reliability

Variable	Default	Description
enable_pod_disruption_budget	false	Protect availability during node upgrades.
pdb_min_available	1	Minimum pods available during voluntary disruptions.
enable_topology_spread / topology_spread_strict	false	Spread pods across zones.

Group 10 — Observability & Health

Variable	Default	Description
startup_probe	TCP, path /status, 30s	Startup probe (port-listening check).
liveness_probe	HTTP /status, 300s delay	Liveness probe against BookStack's unauthenticated health endpoint.
startup_probe_config / health_check_config	App_GKE-level probes	Infrastructure-level probes.
uptime_check_config	disabled	Optional Cloud Monitoring uptime check.
alert_policies	[]	Optional metric alert policies.

Group 11 — Jobs & Scheduled Tasks

Variable	Default	Description
initialization_jobs	[]	Leave empty to use the built-in db-init job.
cron_jobs	[]	Scheduled Kubernetes CronJobs.
additional_services	[]	Sidecar or helper services deployed alongside BookStack.

Group 12 — CI/CD & Binary Authorization

Standard App_GKE Cloud Build / Cloud Deploy integration — see App_GKE. Key inputs: enable_cicd_trigger, github_repository_url, github_token, enable_cloud_deploy, enable_binary_authorization.

Group 13 — Filesystem (NFS)

Variable	Default	Description
enable_nfs	true	Persist uploaded images/attachments on NFS. Disabling loses uploads on redeploy.
nfs_mount_path	/var/lib/bookstack	Mount path where BookStack stores uploads.
nfs_volume_name	nfs-data-volume	Kubernetes volume name for the NFS mount.
nfs_instance_name / nfs_instance_base_name	"" / app-nfs	NFS server discovery/naming.

Group 14 — Cloud Storage & Artifact Registry

Variable	Default	Description
create_cloud_storage	true	Create the default data bucket and any in storage_buckets.
storage_buckets	[{ name_suffix="data" }]	GCS buckets to provision.
gcs_volumes	[]	GCS Fuse volume mounts via the CSI driver.
manage_storage_kms_iam / enable_artifact_registry_cmek	false	CMEK options.
max_images_to_retain	7	Maximum recent Artifact Registry images to keep.
delete_untagged_images	true	Automatically delete untagged images.
image_retention_days	30	Days after which images are eligible for deletion.

Group 15 — Redis Cache & Sessions

Variable	Default	Description
enable_redis	false	Inject REDIS_HOST/REDIS_PORT so BookStack can use Redis for cache/sessions.
redis_host	""	Redis endpoint. Leave empty to use the NFS server IP (requires enable_nfs = true).
redis_port	6379	Redis port.
redis_auth	""	Optional Redis auth password (sensitive).

Group 16 — Database Backend

Variable	Default	Description
database_type	MYSQL_8_0	Fixed — BookStack requires MySQL 8.0.
application_database_name	bookstack	MySQL database name (tenant-prefixed). Immutable after first deploy.
application_database_user	bookstack	Application database user (tenant-prefixed). Immutable after first deploy.
database_password_length	32	Generated password length.
enable_auto_password_rotation	false	Zero-downtime DB password rotation.
rotation_propagation_delay_sec	90	Seconds to wait after rotation before rolling-restarting pods.

Group 17 — Backup & Maintenance

Variable	Default	Description
backup_schedule	0 2 * * *	Automated backup cron (UTC).
backup_retention_days	7	Retention; raise to 30–90 for production/compliance.
enable_backup_import / backup_source / backup_file / backup_format	restore options	Restore from a backup on deploy.

Group 18 — Custom SQL Scripts

enable_custom_sql_scripts, custom_sql_scripts_bucket, custom_sql_scripts_path, custom_sql_scripts_use_root — run SQL from a GCS bucket after provisioning. See App_GKE.

Group 19 — Custom Domain, Static IP & Networking

Variable	Default	Description
enable_custom_domain	true	Provision Ingress for custom hostnames + managed certificate.
application_domains	[]	Hostnames to serve.
reserve_static_ip	true	Stable external IP across redeploys.
network_tags	["nfsserver"]	Node/pod network tags; nfsserver is required when enable_nfs = true.

Group 20 — Identity-Aware Proxy (IAP)

Warning: Enabling IAP requires Google identity authentication for all inbound requests, blocking anonymous readers of the wiki. Only enable IAP when the documentation must not be publicly readable.

Variable	Default	Description
enable_iap	false	Require Google sign-in in front of BookStack.
iap_authorized_users / iap_authorized_groups	[]	Who may access.
iap_oauth_client_id / iap_oauth_client_secret	""	Required when IAP is enabled (sensitive).

Group 21 — Cloud Armor

Variable	Default	Description
enable_cloud_armor	false	Attach a Cloud Armor (WAF) policy to the Ingress backend.
admin_ip_ranges	[]	CIDRs allowed privileged access.
cloud_armor_policy_name	default-waf-policy	Policy name.
enable_cdn	false	Enable Cloud CDN on the GKE Ingress backend.

Group 22 — VPC Service Controls & Audit Logging

Variable	Default	Description
enable_vpc_sc	false	Enforce a VPC-SC perimeter (requires organization_id).
vpc_cidr_ranges / vpc_sc_dry_run	(set)	Access level CIDRs / dry-run mode.
enable_audit_logging	false	Detailed Cloud Audit Logs.

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5. Outputs

These values are returned on a successful deployment and are the quickest way to locate and explore the running resources.

Output	Description
service_name	Kubernetes Service name.
namespace	Namespace the workload runs in.
service_cluster_ip	In-cluster ClusterIP.
stage_service_cluster_ips	Map of ClusterIPs for stage-specific services.
service_external_ip	External LoadBalancer IP (when a static IP is reserved).
service_url	URL to reach BookStack.
database_instance_name	Cloud SQL instance name.
database_name	Application database name.
database_user	Application database user.
database_password_secret	Secret Manager secret holding the DB password.
database_host / database_port	DB endpoint (127.0.0.1 via the Auth Proxy) / port.
storage_buckets	Created Cloud Storage buckets.
network_name / network_exists / regions	VPC network, presence, available regions.
container_image / container_registry	Deployed image and Artifact Registry repo.
monitoring_enabled / monitoring_notification_channels	Monitoring status and channels.
initialization_jobs / db_import_job	Names of the setup and (optional) import jobs.
deployment_id / tenant_id / resource_prefix	Naming identifiers.
project_id / project_number	Project identifiers.
cicd_enabled / cicd_configuration	CI/CD status and details (repo, trigger, registry).
github_repository_url / github_repository_owner / github_repository_name	CI/CD GitHub details.
artifact_registry_repository / cloudbuild_trigger_name / cloudbuild_trigger_id	Registry and build trigger.
kubernetes_ready	Whether the cluster/workload is ready.
vpc_sc_enabled / vpc_sc_perimeter_name / vpc_sc_dry_run_mode	VPC-SC status.
audit_logging_enabled / artifact_registry_cmek_enabled	Audit logging and CMEK status.

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6. Configuration Pitfalls & Sensible Defaults

Risk: Critical (data loss / outage / security) — High (service degraded) — Medium (cost or partial degradation) — Low (minor).

Inherited plan-time validation. This module passes its configuration through the App_GKE foundation engine, which validates values and combinations at plan time — a read replica without its primary, IAP with no authorized identities, a gen1 runtime with NFS/GCS mounts, a database_type that does not match the engine BookStack requires, an out-of-range redis_port/backup_retention_days. Invalid configuration fails the plan with a clear, named error before any resource is created, so most mistakes below are caught up front rather than at apply or runtime.

Setting	Sensible value	Risk	Consequence if wrong
APP_KEY (auto-generated)	Never rotate after first boot	Critical	Rotating it makes all encrypted DB values (two-factor secrets, some settings) permanently undecryptable.
application_database_name / application_database_user	Set once	Critical	Immutable after first deploy; renaming recreates the DB/user and destroys all data.
enable_backup_import	false unless restoring	Critical	Enabling without a valid backup_file fails the import job.
database_type	MYSQL_8_0	Critical	BookStack requires MySQL; any other engine breaks startup.
quota_memory_requests / _limits	binary units (4Gi, 8192Mi)	Critical	Bare integers are bytes and block all pod scheduling in the namespace.
APP_URL	Leave to the module (resolved to the load-balancer URL at deploy time); override via environment_variables only for a custom domain	High	A wrong base URL breaks asset loading, links, and login redirects — BookStack renders unstyled.
enable_nfs	true	High	Disabling loses all uploaded images and attachments on redeploy or pod reschedule.
memory_limit	2Gi	High	Lower values risk OOM kills under concurrent editing and full-text indexing.
enable_cloudsql_volume	true	High	The Auth Proxy sidecar is required for MySQL connectivity on GKE; disabling it breaks DB connectivity (it is not blocked at plan time).
min_instance_count	1	High	GKE requires min ≥ 1; keeping 1 is correct for the NFS-backed single-pod deployment.
max_instance_count	1	High	Multiple pods against the same NFS volume and DB deadlock; do not scale out without external coordination.
session_affinity	ClientIP	High	Without stickiness, UI sessions bounce between pods (only relevant if ever scaled >1).
liveness_probe path	/status (default)	Medium	Pointing the probe at any other path never returns healthy for BookStack — /status is its unauthenticated JSON health endpoint.
enable_iap	only when readers must authenticate	High	IAP blocks all anonymous access, including public documentation readers.
backup_retention_days	7 (raise for prod)	Medium	Too short for compliance retention.

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For the foundation behaviour referenced throughout — IAM and Workload Identity, autoscaling, ingress and certificates, CI/CD, Cloud Armor, IAP, Binary Authorization, VPC-SC, backups, and image mirroring — see App_GKE. BookStack-specific application configuration shared with the Cloud Run variant is described in BookStack_Common.

Related guides

• Hands-on lab: BookStack on GKE — deploy it step by step, with the console screens and commands at each stage.
• BookStack on Google Cloud Run — the same application on Cloud Run, for when you need the other deployment target.
• BookStack Common — Shared Application Configuration — the configuration shared by both deployment targets.