Docker Exec: Access, Commands, and Use Cases

Technical writer

Docker

05.09.2025

Reading time: 6 min

docker exec is a utility that allows you to connect to an already running Docker container and execute commands without restarting or stopping it. This is very convenient for technical analysis, configuration, and debugging applications. For example, you can check logs, modify configurations, or restart services.

And on a cloud server in Hostman, this command helps manage running applications in real time, without rebuilding containers or interfering with the image.

How to Use docker exec: Parameters and Examples

Before using it, make sure Docker is installed and the container is running. If you are just starting out, check out the installation guide for Docker on Ubuntu 22.04.

The basic syntax of docker exec is:

docker exec [options] <container> <command>

Where:

<container> is the name or ID of the target container;
<command> is the instruction to be executed inside it.

Main Parameters:

-i — enables input mode;
-t — attaches a pseudo-terminal, useful for running bash;
-d — runs the task in the background;
-u — allows running the command as a specified user;
-e — sets environment variables;
-w — sets the working directory in which the command will be executed.

Example of launching bash inside a container:

docker exec -it my_container /bin/bash

This way, you can access the container’s environment and run commands directly without stopping it.

Usage Examples

List files inside the container:

ls /app

Run commands with root access:

docker exec -u root my_container whoami

Pass environment variables:

docker exec -e DEBUG=true my_container env

Set working directory:

docker exec -w /var/www my_container ls

Run background tasks:

docker exec -d my_container touch /tmp/testfile

Check Nginx configuration inside a container before restarting it:

docker exec -it nginx_container nginx -t

Advanced Use Cases

Let’s consider some typical but slightly more complex scenarios that may be useful in daily work: running as another user, passing multiple environment variables, specifying a working directory, etc.

Run as web user:

docker exec -u www-data my_container ls -la /var/www

Set multiple environment variables at once:

docker exec -e DEBUG=true -e STAGE=dev my_container env

Set working directory with admin rights:

docker exec -u root -w /opt/app my_container ls

Example with Laravel in Hostman

If you deploy a Laravel application in a container on a Hostman server, docker exec will be very handy. Suppose you have a container with Laravel and a database in a separate service.

To connect to the server:

ssh root@your-server-ip

After connecting, you can run Artisan commands—Laravel’s built-in CLI—inside the container.

Clear application cache:

docker exec -it laravel_app php artisan cache:clear

Run migrations:

docker exec -it laravel_app php artisan migrate

Check queue status:

docker exec -it laravel_app php artisan queue:listen

Set permissions:

docker exec -u www-data -it laravel_app php artisan config:cache

Make a backup of a database deployed in a separate container:

docker exec -it mariadb_container mysqldump -u root -p laravel_db > backup.sql

Before running the last command, make sure that a volume for /backup is mounted, or use SCP to transfer the file to your local machine.

This approach does not require changing the image or direct container access, which makes administration safe and flexible.

Extended Capabilities of docker exec

In this section, we will look at less common but more flexible uses of the docker exec command: for example, running psql in a PostgreSQL container, executing Node.js scripts, or connecting to stopped containers. These cases show how flexible the command can be if something non-standard is required.

The command is not limited to basic tasks: in addition to launching shell or bash, you can work with environments, interact with databases, run Node.js scripts, and connect to any running container.

Connect to PostgreSQL CLI:

docker exec -it postgres_container psql -U postgres -d my_db

Run a Node.js script (if you have script.js):

docker exec -it node_app node script.js

Run a stopped container:

docker start my_container  
docker exec -it my_container bash

Manage users explicitly with -u:

docker exec -u www-data my_container ls -la /var/www

Quickly remove temporary files:

docker exec -it my_container rm -rf /tmp/cache/*

This approach is convenient in cron jobs or when manually cleaning temporary directories.

When Not to Use the Command

Despite its convenience, docker exec is a manual tool for interacting with containers. In production environments, its use can be risky.

Why not use docker exec in production:

Changes are not saved in Dockerfile. This can break reproducibility and infrastructure integrity.
No command logging, so it’s difficult to track actions.
Possible desynchronization with CI/CD pipeline.

Instead, it is recommended to use:

Dockerfile and docker-compose.yml for reproducible builds;
CI/CD for automating tasks via GitHub Actions or GitLab CI;
Monitoring for log processes with Prometheus, Grafana, and Loki.

Troubleshooting Common Errors

No such container

Cause: container not found or stopped

Solution:

docker ps

The command shows a list of running containers. If your container is not listed, it’s not running or hasn’t been created.

exec failed: container not running

Cause: attempt to run a command in a stopped container

Solution:

docker start <container_name>

After starting the container, you can use docker exec again.

permission denied

Cause: insufficient user permissions

Solution:

docker exec -u root <container> <command>

The -u root flag runs the command as root, providing extended access inside the container. This is especially useful when working with system files or configurations.

Difference Between docker exec and docker attach

In addition to docker exec, there is another way to interact with a container—the docker attach command. It connects you directly to the main process running inside the container, as if you launched it in the terminal.

This is convenient if you need to monitor logs or enter data directly, but there are risks: any accidental key press (for example, Ctrl+C) can stop the container. That’s why it’s important to understand the differences.

Also, docker attach requires TTY (a terminal emulator) for correct work with interactive apps like bash or sh.

Parameter	docker exec	docker attach
Requires TTY	Optional	Yes
Multiple connections	Yes	No
Interferes with main process	No	Yes
Usable for debugging	Yes	Partially (may harm app)

Use docker exec for auxiliary tasks—it provides flexibility and reduces risks.

Conclusion

The docker exec command is an effective tool for managing containers without interfering with their lifecycle. It allows you to run commands as different users, pass variables, check logs, and perform administrative tasks.

When working in cloud services such as Hostman, this is especially useful: you can perform targeted actions without rebuilding the image and without risking the main process.

It is important to remember: docker exec is a manual tool and does not replace automated DevOps approaches. For system-level changes, it is better to use Dockerfile and CI/CD, keeping your infrastructure reproducible and secure.

Docker

05.09.2025

Reading time: 6 min

Similar

Docker

Docker Exec: Access, Commands, and Use Cases

How to Use docker exec: Parameters and Examples

Main Parameters:

Usage Examples

Advanced Use Cases

Example with Laravel in Hostman

Extended Capabilities of docker exec

When Not to Use the Command

Troubleshooting Common Errors

No such container

exec failed: container not running

permission denied

Difference Between docker exec and docker attach

Conclusion

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