{"id":48416,"date":"2025-02-08T08:28:26","date_gmt":"2025-02-08T08:28:26","guid":{"rendered":"https:\/\/www.devopsschool.com\/blog\/?p=48416"},"modified":"2025-07-12T05:38:43","modified_gmt":"2025-07-12T05:38:43","slug":"docker-top","status":"publish","type":"post","link":"https:\/\/www.devopsschool.com\/blog\/docker-top\/","title":{"rendered":"Docker commands Guide – docker top with examples"},"content":{"rendered":"\n

Here\u2019s a complete tutorial<\/strong> on docker top<\/code>, covering what it does<\/strong>, examples<\/strong>, and use cases<\/strong>.<\/p>\n\n\n\n

\n\n\n\n

What is docker top<\/code>?<\/strong><\/h2>\n\n\n\n

docker top<\/code> is a Docker command used to display the running processes<\/strong> inside a container. It shows information similar to the ps<\/code> command<\/strong> in Linux, helping you monitor and troubleshoot<\/strong> the container\u2019s processes in real time.<\/p>\n\n\n\n

Key Features:<\/strong><\/h3>\n\n\n\n
    \n
  • Lists all running processes<\/strong> inside a container.<\/li>\n\n\n\n
  • Helps in debugging and monitoring<\/strong> process-level activity.<\/li>\n\n\n\n
  • Supports custom process options<\/strong> like ps<\/code> flags (-ef<\/code> or aux<\/code>).<\/li>\n<\/ul>\n\n\n\n
    \n\n\n\n

    Basic Syntax<\/strong><\/h2>\n\n\n
    docker<\/span> top<\/span> CONTAINER<\/span> [ps OPTIONS]<\/span>\n<\/code><\/span>Code language:<\/span> CSS<\/span> (<\/span>css<\/span>)<\/span><\/small><\/pre>\n\n\n
    Arguments:<\/strong><\/h3>\n\n\n\n
      \n
    • CONTAINER<\/code>: The name or ID of the container.<\/li>\n\n\n\n
    • [ps OPTIONS]<\/code>: Optional Linux ps<\/code> options<\/strong> to customize the output (e.g., -ef<\/code>, aux<\/code>).<\/li>\n<\/ul>\n\n\n\n
      \n\n\n\n
      Examples of docker top<\/code><\/strong><\/h2>\n\n\n\n
      1. List Running Processes in a Container<\/strong><\/h3>\n\n\n
      docker top my_container\n<\/code><\/span><\/pre>\n\n\n
      Example Output:<\/strong><\/p>\n\n\n
      UID     PID   PPID  C  STIME  TTY   TIME   CMD\nroot    123   1     0  10:00  ?     00:00 \/bin\/bash\nroot    456   123   0  10:01  ?     00:00 sleep 300\n<\/code><\/span><\/pre>\n\n\n
      This shows all running processes in my_container<\/code>.<\/p>\n\n\n\n
      \n\n\n\n
      2. Use ps -ef<\/code> to Get Detailed Process Information<\/strong><\/h3>\n\n\n
      docker top my_container -ef\n<\/code><\/span><\/pre>\n\n\n
      This displays detailed process information with extended fields<\/strong>, including UID, PID, CPU, and start time<\/strong>.<\/p>\n\n\n\n
      \n\n\n\n
      3. Display Process Information Similar to ps aux<\/code><\/strong><\/h3>\n\n\n
      docker top my_container aux\n<\/code><\/span><\/pre>\n\n\n
      This provides process information in a format similar to the ps aux<\/code><\/strong> command.<\/p>\n\n\n\n
      \n\n\n\n
      4. Check the Main Process of a Container<\/strong><\/h3>\n\n\n
      docker top my_web_container\n<\/code><\/span><\/pre>\n\n\n
      This helps you verify that the main web server process (e.g., nginx<\/code> or httpd<\/code>) is running as expected.<\/p>\n\n\n\n
      \n\n\n\n
      5. Monitor Resource Usage for a Specific Process<\/strong><\/h3>\n\n\n
      docker top my_app_container -eo pid,cmd,%cpu,%mem\n<\/code><\/span><\/pre>\n\n\n
      This shows the PID, command, CPU usage, and memory usage<\/strong> for processes in my_app_container<\/code>.<\/p>\n\n\n\n
      \n\n\n\n
      6. Use docker top<\/code> in a Script<\/strong><\/h3>\n\n\n
      #!\/bin\/bash<\/span>\ndocker top my_app_container > process_list.txt\necho<\/span> \"Process list saved to process_list.txt\"<\/span>\n<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
      This script saves the process list from my_app_container<\/code> to a file.<\/p>\n\n\n\n
      \n\n\n\n
      7. Check for Zombie Processes<\/strong><\/h3>\n\n\n
      docker top my_container | grep defunct\n<\/code><\/span><\/pre>\n\n\n
      This checks for zombie processes<\/strong> (<defunct><\/code>) inside the container.<\/p>\n\n\n\n
      \n\n\n\n
      8. Combine with watch<\/code> for Real-Time Monitoring<\/strong><\/h3>\n\n\n
      watch docker top my_container\n<\/code><\/span><\/pre>\n\n\n
      This updates the process list every 2 seconds, giving you a real-time view of running processes.<\/p>\n\n\n\n
      \n\n\n\n
      9. Check Processes Across Multiple Containers<\/strong><\/h3>\n\n\n
      docker ps -q | xargs -n 1 docker top\n<\/code><\/span><\/pre>\n\n\n
      This lists processes for all running containers.<\/p>\n\n\n\n
      \n\n\n\n
      Use Cases for docker top<\/code><\/strong><\/h2>\n\n\n\n
      1. Monitoring Running Processes<\/strong><\/h3>\n\n\n\n
        \n
      • Verify that the main application process<\/strong> is running inside the container.<\/li>\n\n\n\n
      • Example: Ensure the web server (NGINX or Apache)<\/strong> is active.<\/li>\n<\/ul>\n\n\n\n
        2. Debugging and Troubleshooting<\/strong><\/h3>\n\n\n\n
          \n
        • Identify stuck or zombie processes<\/strong>.<\/li>\n\n\n\n
        • Debug performance issues by checking which processes consume high CPU or memory<\/strong>.<\/li>\n<\/ul>\n\n\n\n
          3. Security Auditing<\/strong><\/h3>\n\n\n\n
            \n
          • Monitor processes to detect unauthorized or malicious processes<\/strong> inside containers.<\/li>\n\n\n\n
          • Example: Ensure only the intended processes are running in production containers.<\/li>\n<\/ul>\n\n\n\n
            4. Incident Response and Forensics<\/strong><\/h3>\n\n\n\n
              \n
            • Use docker top<\/code> during incident response to capture the state of processes in a compromised container.<\/li>\n<\/ul>\n\n\n\n
              5. Performance Analysis<\/strong><\/h3>\n\n\n\n
                \n
              • Identify bottlenecks by monitoring the CPU and memory usage of container processes.<\/li>\n\n\n\n
              • Example: Check if a background task is consuming too many resources.<\/li>\n<\/ul>\n\n\n\n
                6. Process-Based Monitoring and Health Checks<\/strong><\/h3>\n\n\n\n
                  \n
                • Integrate docker top<\/code> in monitoring scripts to detect missing or stuck processes.<\/li>\n\n\n\n
                • Example: Automatically restart a container if a key process is missing.<\/li>\n<\/ul>\n\n\n\n
                  \n\n\n\n
                  List of Common docker top<\/code> Commands<\/strong><\/h2>\n\n\n\n
                  Command<\/strong><\/th>Description<\/strong><\/th><\/tr><\/thead>
                  docker top my_container<\/code><\/td>List all processes running in my_container<\/code><\/td><\/tr>
                  docker top my_container -ef<\/code><\/td>Show detailed process information (ps -ef<\/code>)<\/td><\/tr>
                  docker top my_container aux<\/code><\/td>Display process info in ps aux<\/code> format<\/td><\/tr>
                  `docker top my_container<\/td>grep sleep`<\/td><\/tr>
                  docker top my_app_container -eo pid,cmd,%cpu,%mem<\/code><\/td>Show specific columns (PID, command, CPU, memory)<\/td><\/tr>
                  `docker ps -q<\/td>xargs -n 1 docker top`<\/td><\/tr>
                  watch docker top my_container<\/code><\/td>Monitor container processes in real time<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
                  \n\n\n\n
                  Best Practices for Using docker top<\/code>:<\/strong><\/h2>\n\n\n\n
                    \n
                  1. Use docker top<\/code> for regular monitoring<\/strong> to verify critical processes.<\/li>\n\n\n\n
                  2. Combine with grep<\/code> or watch<\/code><\/strong> for real-time process filtering and monitoring.<\/li>\n\n\n\n
                  3. Automate health checks<\/strong> based on process availability and resource consumption.<\/li>\n\n\n\n
                  4. Filter columns (-eo<\/code>)<\/strong> for relevant metrics like CPU, memory, and PID.<\/li>\n\n\n\n
                  5. Capture process lists<\/strong> during debugging or incident response for later analysis.<\/li>\n<\/ol>\n\n\n\n
                    \n\n\n\n
                    Common Errors and Solutions<\/strong><\/h2>\n\n\n\n
                      \n
                    1. “No such container”<\/strong>
                      \u2192 Ensure the container exists and is running. Use docker ps<\/code> to verify.<\/li>\n\n\n\n
                    2. Processes not shown<\/strong>
                      \u2192 The container may have stopped or exited. Use docker ps -a<\/code> to check its status.<\/li>\n\n\n\n
                    3. Zombie processes detected (<defunct><\/code>)<\/strong>
                      \u2192 Investigate the main process or entrypoint script for mismanagement of child processes.<\/li>\n<\/ol>\n\n\n\n
                      \n\n\n\n
                      Combining docker top<\/code> with Other Commands<\/strong><\/h2>\n\n\n\n
                        \n
                      1. Check Resource Usage with docker stats<\/code>:<\/strong> docker stats my_container docker top my_container<\/code><\/li>\n\n\n\n
                      2. Restart Container if a Process is Missing:<\/strong> if ! docker top my_app | grep \"nginx\"; then docker restart my_app fi<\/code><\/li>\n<\/ol>\n\n\n\n
                        \n\n\n\n
                        <\/p>\n","protected":false},"excerpt":{"rendered":"
                        Here\u2019s a complete tutorial on docker top, covering what it does, examples, and use cases. What is docker top? docker top is a Docker command used to display the running… <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_joinchat":[],"footnotes":""},"categories":[4862],"tags":[],"class_list":["post-48416","post","type-post","status-publish","format-standard","hentry","category-docker"],"_links":{"self":[{"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/posts\/48416","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/comments?post=48416"}],"version-history":[{"count":2,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/posts\/48416\/revisions"}],"predecessor-version":[{"id":48418,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/posts\/48416\/revisions\/48418"}],"wp:attachment":[{"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/media?parent=48416"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/categories?post=48416"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/tags?post=48416"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}