added downgrade capability to installer script

- added --list to show available node versions
- added --version to install a particular node version
- made script more robust (file checks, command installs)
- updated tutorial with downgrade process

Author: jpop32

build/tutorials/nodes-and-staking/set-up-node-with-installer.md

@@ -59,7 +59,7 @@ So, now that you prepared your system and have the info ready, let's get to it.
 
 To download and run the script, enter the following in the terminal:
 
-```text
+```bash
 wget -nd -m https://raw.githubusercontent.com/ava-labs/avalanche-docs/master/scripts/avalanchego-installer.sh;\
 chmod 755 avalanchego-installer.sh;\
 ./avalanchego-installer.sh
@@ -125,7 +125,7 @@ The script is finished, and you should see the system prompt again.
 
 AvalancheGo should be running in the background as a service. You can check that it's running with:
 
-```text
+```bash
 sudo systemctl status avalanchego
 ```
 
@@ -157,7 +157,7 @@ Note the `active (running)` which indicates the service is running ok. You may n
 
 To find out your NodeID, which is used to identify your node to the network, run the following command:
 
-```text
+```bash
 sudo journalctl -u avalanchego | grep "node's ID"
 ```
 
@@ -171,7 +171,7 @@ Prepend `NodeID-` to the value to get, for example, `NodeID-6seStrauyCnVV7NEVwRb
 
 Your node should be in the process of bootstrapping now. You can monitor the progress by issuing the following command:
 
-```text
+```bash
 sudo journalctl -u avalanchego -f
 ```
 
@@ -181,13 +181,13 @@ Press `ctrl+C` when you wish to stop reading node output.
 
 To stop AvalancheGo, run:
 
-```text
+```bash
 sudo systemctl stop avalanchego
 ```
 
 To start it again, run:
 
-```text
+```bash
 sudo systemctl start avalanchego
 ```
 
@@ -203,7 +203,7 @@ It is recommended to always upgrade to the latest version, because new versions
 
 To upgrade your node, just run the installer script again:
 
-```text
+```bash
 ./avalanchego-installer.sh
 ```
 
@@ -227,6 +227,47 @@ avalanche/1.1.1 [network=mainnet, database=v1.0.0, commit=f76f1fd5f99736cf468413
 Done!
 ```
 
+## Downgrade to a previous version
+
+Bugs do occur, even with quality control involving strict testing. It may so happen that the newly released build is broken for a given architecture, or in a particular context. Check the official communication channels and team Discord for more information. If it turns out the problem really is with the newly released version, and the recommended solution is to return to the previous node version, installer script can help you in that situation too.
+
+To see a list of available node versions for installation, run:
+
+```bash
+./avalanchego-installer.sh --list
+```
+It will print out a list, something like:
+
+```text
+AvalancheGo installer
+---------------------
+Available versions:
+v1.3.2
+v1.3.1
+v1.3.0
+v1.2.4-arm-fix
+v1.2.4
+v1.2.3-signed
+v1.2.3
+v1.2.2
+v1.2.1
+v1.2.0
+```
+
+Note the version you need to install to get the node to a known good configuration, and then run the installer with `--version` flag followed by the tag of the version you wish to install. For example:
+
+```bash
+./avalanchego-installer.sh --version v1.3.1
+```
+
+Command will start the upgrade process using the node version specified.
+
+{% hint style="danger" %}
+Do not downgrade your node version without explicit advice from the team to do so! Running an outdated version may lead to incompatibilities that may hinder your node and network performance, and may result in your node being banned by other nodes, potentially risking your staking rewards!
+{% endhint %}
+
+Thanks to community member [Jean Zundel](https://github.com/jzu) for motivation and script for node downgrade.
+
 ## What next?
 
 That's it, you're running an AvalancheGo node! Congratulations! Let us know you did it on our [Twitter](https://twitter.com/avalancheavax), [Telegram](https://t.me/avalancheavax) or [Reddit](https://t.me/avalancheavax)!

scripts/avalanchego-installer.sh

@@ -27,18 +27,69 @@ create_service_file () {
   echo "">>avalanchego.service
 }
 
-#helper function to check for presence of curl, and install if missing
-check_curl() {
+#helper function to check for presence of required commands, and install if missing
+check_reqs () {
 if ! command -v curl &> /dev/null
 then
     echo "curl could not be found, will install..."
     sudo apt-get install curl -y
 fi
+if ! command -v wget &> /dev/null
+then
+    echo "wget could not be found, will install..."
+    sudo apt-get install wget -y
+fi
+if ! command -v dig &> /dev/null
+then
+    echo "dig could not be found, will install..."
+    sudo apt-get install dnsutils -y
+fi
+}
+
+#helper function that prints usage
+usage () {
+echo "Usage: $0 [--list] [--version <tag>] [--help]"
+echo ""
+echo "Options:"
+echo "   --help            Shows this message"
+echo "   --list            Lists 10 newest versions available to install"
+echo "   --version <tag>   Installs <tag> version"
+echo ""
+echo "Ran without any options, script will install or upgrade AvalancheGo to latest available version."
+echo ""
+exit 0
 }
 
 echo "AvalancheGo installer"
 echo "---------------------"
+
+if [ $# -ne 0 ] #arguments check
+then
+  case $1 in
+    --list) #print version list and exit (last 10 versions)
+      echo "Available versions:"
+      wget -q -O - https://api.github.com/repos/ava-labs/avalanchego/releases \
+      | grep tag_name \
+      | sed 's/.*: "\(.*\)".*/\1/' \
+      | head
+      exit 0
+      ;;
+    --version) #explicit version selection
+      if [ $# -eq 2 ]
+      then
+        version=$2
+      else
+        usage
+      fi
+      ;;
+    *)
+      usage
+      ;;
+  esac
+fi
+
 echo "Preparing environment..."
+check_reqs
 foundIP="$(dig +short myip.opendns.com @resolver1.opendns.com)"
 foundArch="$(uname -m)"                         #get system architecture
 foundOS="$(uname)"                              #get OS
@@ -60,7 +111,6 @@ else
   echo "Exiting."
   exit
 fi
-check_curl
 if test -f "/etc/systemd/system/avalanchego.service"; then
   foundAvalancheGo=true
   echo "Found AvalancheGo systemd service already installed, switching to upgrade mode."
@@ -74,16 +124,16 @@ mkdir -p /tmp/avalanchego-install               #make a directory to work in
 rm -rf /tmp/avalanchego-install/*               #clean up in case previous install didn't
 cd /tmp/avalanchego-install
 
-read -p "Press enter to install the latest AvalancheGo version, or specify the version to install (e.g. v1.2.3): " version
 version=${version:-latest}
 echo "Looking for $getArch version $version..."
 if [ "$version" = "latest" ]; then
   fileName="$(curl -s https://api.github.com/repos/ava-labs/avalanchego/releases/latest | grep "avalanchego-linux-$getArch.*tar\(.gz\)*\"" | cut -d : -f 2,3 | tr -d \" | cut -d , -f 2)"
 else
   fileName="https://github.com/ava-labs/avalanchego/releases/download/$version/avalanchego-linux-$getArch-$version.tar.gz"
 fi
-
-if [ "$fileName" = "" ]; then
+if [[ `wget -S --spider $fileName  2>&1 | grep 'HTTP/1.1 200 OK'` ]]; then
+  echo "Node version found."
+else
   echo "Unable to find AvalancheGo version $version. Exiting."
   if [ "$foundAvalancheGo" = "true" ]; then
     echo "Restarting service..."