Running Commands on Remote Server via SSH

#!/bin/bash

# --- Configuration ---
REMOTE_USER="webadmin"
REMOTE_HOST="your_remote_server.com" # Replace with your server IP or hostname
SSH_PORT=22                         # Default SSH port

# Ensure passwordless SSH is set up (e.g., ssh-copy-id)
# ssh-keygen -t rsa -b 4096
# ssh-copy-id -p $SSH_PORT $REMOTE_USER@$REMOTE_HOST

# --- Functions ---
log_message() {
    local type=$1
    local message=$2
    echo "[$(date +'%Y-%m-%d %H:%M:%S')] [$type] $message"
}

# Function to execute a command remotely
execute_remote_command() {
    local command="$1"
    log_message INFO "Executing remote command on $REMOTE_HOST: '$command'"
    ssh -p "$SSH_PORT" "$REMOTE_USER@$REMOTE_HOST" "$command"
    local exit_code=$?
    if [ $exit_code -ne 0 ]; then
        log_message ERROR "Remote command failed with exit code $exit_code."
        return 1
    fi
    return 0
}

# Function to upload a file to the remote server
upload_file() {
    local local_path="$1"
    local remote_path="$2"
    log_message INFO "Uploading $local_path to $REMOTE_HOST:$remote_path"
    scp -P "$SSH_PORT" "$local_path" "$REMOTE_USER@$REMOTE_HOST:$remote_path"
    local exit_code=$?
    if [ $exit_code -ne 0 ]; then
        log_message ERROR "File upload failed with exit code $exit_code."
        return 1
    fi
    return 0
}

# Function to download a file from the remote server
download_file() {
    local remote_path="$1"
    local local_path="$2"
    log_message INFO "Downloading $REMOTE_HOST:$remote_path to $local_path"
    scp -P "$SSH_PORT" "$REMOTE_USER@$REMOTE_HOST:$remote_path" "$local_path"
    local exit_code=$?
    if [ $exit_code -ne 0 ]; then
        log_message ERROR "File download failed with exit code $exit_code."
        return 1
    fi
    return 0
}

# --- Main Script ---
log_message INFO "Script started."

# Example 1: Check remote disk usage
if ! execute_remote_command "df -h"; then
    log_message ERROR "Failed to get remote disk usage."
    exit 1
fi

# Example 2: Create a dummy file locally and upload it
echo "This is a test file from local." > local_test_file.txt
if upload_file "local_test_file.txt" "/tmp/remote_test_file.txt"; then
    log_message INFO "File uploaded successfully. Verifying remote existence..."
    execute_remote_command "cat /tmp/remote_test_file.txt"
else
    log_message ERROR "Failed to upload file."
    rm local_test_file.txt
    exit 1
fi
rm local_test_file.txt

# Example 3: Download a remote file (e.g., /etc/hostname)
if download_file "/etc/hostname" "downloaded_hostname.txt"; then
    log_message INFO "Remote hostname downloaded successfully. Content:"
    cat downloaded_hostname.txt
else
    log_message ERROR "Failed to download remote hostname."
    rm -f downloaded_hostname.txt
    exit 1
fi
rm -f downloaded_hostname.txt

# Example 4: Restart a service (use with caution!)
# if execute_remote_command "sudo systemctl restart nginx"; then
#     log_message INFO "Nginx restarted successfully."
# else
#     log_message ERROR "Failed to restart Nginx."
#     exit 1
# fi

log_message INFO "Script finished."