Added Steps for Upgrading Devtron using Kubectl for 0.3.x (#1459)

Author: gunish-dt

docs/setup/upgrade/devtron-upgrade-0.3.x-0.3.x.md

@@ -6,7 +6,7 @@ If you want to check the current version of Devtron you are using, please use th
 kubectl -n devtroncd get installers installer-devtron -o jsonpath='{.status.sync.data}' | grep "^LTAG=" | cut -d"=" -f2-
 ```
 
-## Follow the below mentioned steps to upgrade the Devtron version
+## Follow the below mentioned steps to upgrade the Devtron version using Helm
 
 1. Fetch the latest Devtron helm chart
 
@@ -25,3 +25,18 @@ DEVTRON_TARGET_VERSION=v0.3.x
 ```bash
 helm upgrade devtron devtron/devtron-operator --namespace devtroncd --set installer.release=$DEVTRON_TARGET_VERSION
 ```
+
+
+## Follow the below mentioned steps to upgrade the Devtron version using Kubectl
+
+1. Input the target Devtron version that you want to upgrade to. You can find the latest releases from Devtron on Github https://github.com/devtron-labs/devtron/releases
+
+```bash
+DEVTRON_TARGET_VERSION=v0.3.x
+```
+
+2. Patch Devtron Installer
+
+```bash
+kubectl patch -n devtroncd installer installer-devtron --type='json' -p='[{"op": "add", "path": "/spec/reSync", "value": true },{"op": "replace", "path": "/spec/url", "value": "https://raw.githubusercontent.com/devtron-labs/devtron/$DEVTRON_TARGET_VERSION/manifests/installation-script"}]'
+```