{"id":48357,"date":"2025-02-08T08:11:28","date_gmt":"2025-02-08T08:11:28","guid":{"rendered":"https:\/\/www.devopsschool.com\/blog\/?p=48357"},"modified":"2025-07-12T05:38:46","modified_gmt":"2025-07-12T05:38:46","slug":"docker-diff","status":"publish","type":"post","link":"https:\/\/www.devopsschool.com\/blog\/docker-diff\/","title":{"rendered":"Docker commands Guide – docker diff with examples"},"content":{"rendered":"\n

Here\u2019s a complete tutorial<\/strong> on the docker diff<\/code> command, explaining how it works, its purpose, and providing a comprehensive list of examples.<\/p>\n\n\n\n

\n\n\n\n

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

docker diff<\/code> is a Docker command used to inspect changes made to the filesystem<\/strong> of a container. It shows the differences between the container’s current state<\/strong> and its original image<\/strong>.<\/p>\n\n\n\n

Key Features:<\/strong><\/h3>\n\n\n\n
    \n
  • Lists changes to the container’s filesystem<\/strong>.<\/li>\n\n\n\n
  • Helps in debugging<\/strong> and auditing<\/strong> what files have been added, modified, or deleted in the container.<\/li>\n\n\n\n
  • Useful for verifying the impact of commands executed inside a running container.<\/li>\n<\/ul>\n\n\n\n
    \n\n\n\n

    Basic Syntax<\/strong><\/h2>\n\n\n
    docker<\/span> diff<\/span> [OPTIONS]<\/span> CONTAINER<\/span>\n<\/code><\/span>Code language:<\/span> CSS<\/span> (<\/span>css<\/span>)<\/span><\/small><\/pre>\n\n\n
    Options:<\/strong><\/h3>\n\n\n\n
    There are no specific options for docker diff<\/code>. You simply provide the container name or ID<\/strong>.<\/p>\n\n\n\n
    \n\n\n\n
    Output Explanation<\/strong><\/h2>\n\n\n\n
    docker diff<\/code> provides three types of changes:<\/p>\n\n\n\n
      \n
    • A<\/strong> \u2192 File or directory was added<\/strong> to the container.<\/li>\n\n\n\n
    • C<\/strong> \u2192 File or directory was changed<\/strong> (modified).<\/li>\n\n\n\n
    • D<\/strong> \u2192 File or directory was deleted<\/strong> from the container.<\/li>\n<\/ul>\n\n\n\n
      Example Output:<\/h3>\n\n\n
      C \/etc\/hostname\nA \/new_file.txt\nD \/tmp\/old_log.txt\n<\/code><\/span><\/pre>\n\n\n
        \n
      • C \/etc\/hostname<\/code> \u2192 \/etc\/hostname<\/code> was modified.<\/li>\n\n\n\n
      • A \/new_file.txt<\/code> \u2192 new_file.txt<\/code> was added to the container.<\/li>\n\n\n\n
      • D \/tmp\/old_log.txt<\/code> \u2192 old_log.txt<\/code> was deleted from \/tmp<\/code>.<\/li>\n<\/ul>\n\n\n\n
        \n\n\n\n
        Examples of docker diff<\/code><\/strong><\/h2>\n\n\n\n
        1. Check Changes in a Running Container<\/strong><\/h3>\n\n\n
        docker diff my_container\n<\/code><\/span><\/pre>\n\n\n
        This command shows all changes to the my_container<\/code> filesystem.<\/p>\n\n\n\n
        \n\n\n\n
        2. Check Changes After Modifying a File<\/strong><\/h3>\n\n\n\n
          \n
        1. Start a container: docker run -dit --name my_ubuntu ubuntu<\/code><\/li>\n\n\n\n
        2. Modify or create a file in the container: docker exec my_ubuntu bash -c \"echo 'Hello Docker' > \/tmp\/hello.txt\"<\/code><\/li>\n\n\n\n
        3. Run docker diff<\/code> to check the change: docker diff my_ubuntu<\/code> Output:<\/strong> A \/tmp\/hello.txt<\/code><\/li>\n<\/ol>\n\n\n\n
          \n\n\n\n
          3. Detect Deleted Files<\/strong><\/h3>\n\n\n\n
            \n
          1. Start a container: docker run -dit --name my_nginx nginx<\/code><\/li>\n\n\n\n
          2. Delete a file inside the container: docker exec my_nginx rm \/etc\/nginx\/conf.d\/default.conf<\/code><\/li>\n\n\n\n
          3. Run docker diff<\/code>: docker diff my_nginx<\/code> Output:<\/strong> D \/etc\/nginx\/conf.d\/default.conf<\/code><\/li>\n<\/ol>\n\n\n\n
            \n\n\n\n
            4. Monitor Changes in a Container’s Temporary Files<\/strong><\/h3>\n\n\n\n
            Containers often generate temporary files in \/tmp<\/code> or \/var<\/code> during operation. You can use docker diff<\/code> to track these changes:<\/p>\n\n\n
            docker diff my_temp_container\n<\/code><\/span><\/pre>\n\n\n
            This helps identify logs or cache files added during runtime.<\/p>\n\n\n\n
            \n\n\n\n
            5. Check Changes in a Stopped Container<\/strong><\/h3>\n\n\n\n
            You can run docker diff<\/code> on both running and stopped containers:<\/p>\n\n\n
            docker diff stopped_container\n<\/code><\/span><\/pre>\n\n\n
            \n\n\n\n
            6. Debugging File Changes in a Database Container<\/strong><\/h3>\n\n\n\n
            If you’re running a MySQL container and suspect that files in \/var\/lib\/mysql<\/code> have been modified:<\/p>\n\n\n
            docker diff my_mysql\n<\/code><\/span><\/pre>\n\n\n
            This will list all changes in the \/var\/lib\/mysql<\/code> directory, helping you verify data persistence or accidental modifications.<\/p>\n\n\n\n
            \n\n\n\n
            7. Combine docker diff<\/code> with Other Commands<\/strong><\/h3>\n\n\n\n
            Using docker diff<\/code> with docker exec<\/code><\/strong><\/h4>\n\n\n\n
            To confirm a change detected by docker diff<\/code>, use docker exec<\/code>:<\/p>\n\n\n
            docker exec my_container cat \/path\/to\/file\n<\/code><\/span><\/pre>\n\n\n
            Using docker diff<\/code> with docker commit<\/code><\/strong><\/h4>\n\n\n\n
            If you want to save a modified container after detecting changes:<\/p>\n\n\n
            docker commit my_container my_new_image\n<\/code><\/span><\/pre>\n\n\n
            \n\n\n\n
            List of Common docker diff<\/code> Commands<\/strong><\/h2>\n\n\n\n
            Command<\/strong><\/th>Description<\/strong><\/th><\/tr><\/thead>
            docker diff my_container<\/code><\/td>Show all changes in the container\u2019s filesystem<\/td><\/tr>
            docker diff stopped_container<\/code><\/td>Inspect changes in a stopped container<\/td><\/tr>
            docker diff my_nginx<\/code><\/td>Check changes in an NGINX container<\/td><\/tr>
            docker diff my_database<\/code><\/td>Monitor changes in a database container<\/td><\/tr>
            docker diff container_id<\/code><\/td>Use container ID to check for filesystem changes<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
            \n\n\n\n
            Best Practices for docker diff<\/code>:<\/strong><\/h2>\n\n\n\n
              \n
            1. Use docker diff<\/code> for debugging<\/strong> unexpected behavior in containers.<\/li>\n\n\n\n
            2. Combine with docker commit<\/code><\/strong> to create a new image from a modified container.<\/li>\n\n\n\n
            3. Regularly monitor changes<\/strong> in critical containers (e.g., databases, web servers).<\/li>\n\n\n\n
            4. Avoid leaving unnecessary files<\/strong> in containers\u2014docker diff<\/code> helps track them.<\/li>\n<\/ol>\n\n\n\n
              \n\n\n\n
              Common Errors and Solutions<\/strong><\/h2>\n\n\n\n
                \n
              1. “Error response from daemon: No such container”<\/strong>
                \u2192 Ensure the container name or ID is correct and the container exists.<\/li>\n\n\n\n
              2. “No changes detected”<\/strong>
                \u2192 This means no changes have been made since the container was created.<\/li>\n\n\n\n
              3. Permission Denied Errors<\/strong>
                \u2192 Ensure you have the necessary permissions to inspect the container.<\/li>\n<\/ol>\n\n\n\n
                \n\n\n\n
                <\/p>\n","protected":false},"excerpt":{"rendered":"
                Here\u2019s a complete tutorial on the docker diff command, explaining how it works, its purpose, and providing a comprehensive list of examples. What is docker diff? docker diff is a… <\/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-48357","post","type-post","status-publish","format-standard","hentry","category-docker"],"_links":{"self":[{"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/posts\/48357","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=48357"}],"version-history":[{"count":2,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/posts\/48357\/revisions"}],"predecessor-version":[{"id":48359,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/posts\/48357\/revisions\/48359"}],"wp:attachment":[{"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/media?parent=48357"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/categories?post=48357"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.devopsschool.com\/blog\/wp-json\/wp\/v2\/tags?post=48357"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}