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landing/docs/Bash-Scripts/017-executing-bash-script-on-multiple-remote-server.md

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+# Running On Multiple Servers
+
+Automate script execution across multiple remote servers. Instead of manual copying and logging in, learn to run Bash scripts on many machines with a single command.
+
+### Prerequisites
+
+You'll need a few remote Linux servers with **SSH access**. Gather their **IP addresses** or **hostnames** and list them in a file named `servers.txt`, one per line.
+
+Create `servers.txt`:
+
+```bash
+touch servers.txt
+```
+
+Open `servers.txt` and add your server details:
+
+```
+your_server_ip_1
+your_server_ip_2
+your_server_ip_3
+```
+
+---
+
+### The Script for Remote Execution
+
+We'll use a simple Bash script that performs basic server checks: memory, CPU, TCP connections, and kernel version. Create a file named `remote_check.sh` and add the following content:
+
+```bash
+touch remote_check.sh
+```
+
+Open `remote_check.sh` and add:
+
+```bash
+#!/usr/bin/env bash
+
+##
+# Server status script:
+#   - Memory usage
+#   - CPU load
+#   - Number of TCP connections
+#   - Kernel version
+##
+
+server_name=$(hostname)
+
+function memory_check() {
+    echo "#######"
+    echo "The current memory usage on ${server_name} is: "
+    free -h
+    echo "#######"
+}
+
+function cpu_check() {
+    echo "#######"
+    echo "The current CPU load on ${server_name} is: "
+    echo ""
+    uptime
+    echo "#######"
+}
+
+function tcp_check() {
+    echo "#######"
+    echo "Total TCP connections on ${server_name}: "
+    echo ""
+    cat /proc/net/tcp | wc -l
+    echo "#######"
+}
+
+function kernel_check() {
+    echo "#######"
+    echo "The exact Kernel version on ${server_name} is: "
+    echo ""
+    uname -r
+    echo "#######"
+}
+
+function all_checks() {
+    memory_check
+    cpu_check
+    tcp_check
+    kernel_check
+}
+
+all_checks
+```
+
+---
+
+### Execute on Remote Servers
+
+With `remote_check.sh` and `servers.txt` ready, run the following single command. This loop iterates through each server, using **SSH** to execute the script without local file transfer or manual logins.
+
+```bash
+for server in $(cat servers.txt); do ssh your_user@"${server}" 'bash -s' < ./remote_check.sh; done
+```
+
+**Breakdown:**
+* `for server in $(cat servers.txt)`: Reads each IP/hostname from `servers.txt` into the `server` variable.
+* `ssh your_user@"${server}"`: Connects to the remote server via SSH as `your_user`.
+* `'bash -s'`: Executes a Bash shell on the remote server, reading commands from standard input.
+* `< ./remote_check.sh`: Redirects the local `remote_check.sh` script's content to the remote Bash shell's standard input.
+
+Each server will then execute the script, printing its status checks directly to your local terminal.
+
+---
+
+### Conclusion
+
+This method efficiently executes Bash scripts across multiple remote servers. It avoids manual file transfers and individual logins, proving scalable for more complex scripts and larger environments. For extensive, state-managed automation, dedicated tools are often recommended.
+
+> {notice} This content was inspired by a piece by softwareshinobi on Dev Team Six.