Add helm offline installation instruction

Author: michaellzc

docs/admin/deploy/kubernetes/index.mdx

@@ -1021,16 +1021,18 @@ When all pods have restarted and show as Running, you can browse to your Sourceg
 
 **Step 2:**
 
-> <Callout type="warning">
-> 	The Kubernetes Helm deployment type does not support MVU from Sourcegraph
-> 	`v5.9.45` versions and earlier to ANY version `v6.0.x` or later. Admins
-> 	seeking to upgrade to any Sourcegraph version `v6.0.x` or later (including
-> 	`v6.1.x`, `v6.2.x`, etc.) must first upgrade to `v5.10.3940` or
-> 	`v5.11.6271` and then use the standard upgrade procedure to get to their
-> 	target version. This is because migrator in all versions from `v6.0.0`
-> 	onwards will no longer connect to Postgres 12 databases. For more info see
-> 	our [PostgreSQL upgrade docs](/admin/postgres#requirements).
-> </Callout>
+<Callout type="warning">
+
+    The Kubernetes Helm deployment type does not support MVU from Sourcegraph
+    `v5.9.45` versions and earlier to ANY version `v6.0.x` or later. Admins
+    seeking to upgrade to any Sourcegraph version `v6.0.x` or later (including
+    `v6.1.x`, `v6.2.x`, etc.) must first upgrade to `v5.10.3940` or
+    `v5.11.6271` and then use the standard upgrade procedure to get to their
+    target version. This is because migrator in all versions from `v6.0.0`
+    onwards will no longer connect to Postgres 12 databases. For more info see
+    our [PostgreSQL upgrade docs](/admin/postgres#requirements).
+
+</Callout>
 
 Scale down `deployments` and `statefulSets` that access the database, _this step prevents services from accessing the database while schema migrations are in process._
 The following services must have their replicas scaled to 0:
@@ -1049,13 +1051,15 @@ The following convenience commands provide an example of scaling down the necess
 
 Deployments:
 
-````sh
+```sh
 $ kubectl get -n sourcegraph deploy --no-headers | awk '{print $1}' | xargs -n 1 -P 8 -I % kubectl -n sourcegraph scale deployment % --replicas=0
-   ```
+```
+
 StatefulSets:
+
 ```sh
 $ kubectl -n sourcegraph get sts --selector 'app.kubernetes.io/component!=codeinsights-db,app.kubernetes.io/component!=codeintel-db,app.kubernetes.io/component!=pgsql' --no-headers | awk '{print $1}' | xargs -n 1 -P 8 -I % kubectl -n sourcegraph scale sts % --replicas=0
-````
+```
 
 <Callout type="note">
 	The commands above use the `sourcegraph` namespace and are specific to the
@@ -1078,7 +1082,7 @@ $ helm upgrade --install -n <your namespace> --set "migrator.args={upgrade,--fro
 
 **Example:**
 
-````sh
+```sh
 $ helm upgrade --install -n sourcegraph --set "migrator.args={upgrade,--from=3.41.0,--to=4.5.1}" sourcegraph-migrator sourcegraph/sourcegraph-migrator --version {CURRENT_VERSION_NO_V}
 Release "sourcegraph-migrator" has been upgraded. Happy Helming!
 NAME: sourcegraph-migrator
@@ -1091,7 +1095,7 @@ TEST SUITE: None
 👉 Migrating to v4.5 (step 3 of 3)
 👉 Running schema migrations
 ✅ Schema migrations complete
-    ```
+```
 
 You can learn more about running migrator operations in helm in the [migrator operations doc](/admin/updates/migrator/migrator-operations#kubernetes-helm).
 
@@ -1101,15 +1105,15 @@ Now that the databases have been migrated to the latest versions, services can b
 
 ```sh
 $ helm upgrade -n <your namespace> --install -f override.yaml --version <sourcegraph version> sourcegraph sourcegraph/sourcegraph
-    ```
+```
 
 ### Rollback
 
 You can revert to a previous version with the following command:
 
 ```sh
 $ helm rollback sourcegraph
-````
+```
 
 If you are rolling back more than a single version, then you must also [roll back your database](/admin/how-to/rollback_database), as database migrations (which may have run at some point during the upgrade) are guaranteed to be compatible with one previous minor version.
 
@@ -1121,6 +1125,30 @@ In some situations, administrators may wish to migrate their databases before up
 
 To execute the database migrations independently, you can use the [Sourcegraph Migrator] helm chart.
 
+## Using Helm in restricted environment
+
+Some customers may not be allowed to directly install applications from a remote Helm Registry. In these cases, you may choose to download the chart to inspect the content, then install it locally.
+
+It's recommended to commit your charts in a VCS repo and namespace by versions:
+
+```
+charts/
+  sourcegraph-6.1.0/
+  sourcegraph-6.2.0/
+```
+
+Download and untar to a specific directory at `charts/sourcegraph-$VERSION`:
+
+```sh
+$ helm pull sourcegraph/sourcegraph --version $VERSION --untar -d charts/sourcegraph-$VERSION
+```
+
+Then, you can install the chart from the local directory:
+
+```sh
+$ helm upgrade --install sourcegraph charts/sourcegraph-$VERSION
+```
+
 ## Reviewing Changes
 
 When configuring an override file or performing an upgrade, we recommend reviewing the changes before applying them.