When automating Docker container management, you often need to programmatically set the root password. While Docker best practices suggest baking credentials into images, sometimes you need runtime password changes - especially for SSH containers.



The sshpass method you tried faces multiple issues:


SSH servers often block password changes over SSH for security
The passwd command expects interactive terminal input
Container networking might not be ready when your script runs




1. Using Docker Exec with chpasswd

The most robust solution using docker exec:

# Single command version
docker exec -i container_name bash -c \
"echo 'root:NEWPASSWORD' | chpasswd"

# Alternative with password confirmation
docker exec -i container_name bash -c \
"echo -e 'NEWPASSWORD\\nNEWPASSWORD' | passwd root"

2. During Container Startup
Modify your docker run command:
docker run -d --name my_container \
-e ROOT_PASSWORD=mysecurepass \
my_image /bin/bash -c \
"echo root:\$ROOT_PASSWORD | chpasswd && /usr/sbin/sshd -D"

3. Using Dockerfile (For Build-Time)
Though you prefer runtime changes, here's the Dockerfile approach for completeness:
FROM ubuntu:latest
RUN apt-get update && apt-get install -y openssh-server
RUN echo 'root:INITIALPASS' | chpasswd
COPY setpassword.sh /
RUN chmod +x /setpassword.sh
ENTRYPOINT ["/setpassword.sh"]


Always verify container is running before executing commands
Use docker logs to check for errors
Consider adding sleep before commands if containers boot slowly
For production, use SSH keys instead of password authentication

When implementing this:

Never hardcode passwords in scripts
Use environment variables or secrets management
Rotate passwords regularly
Consider disabling root SSH access entirely



When automating Docker container management, you might need to change the root password programmatically. While the Docker way suggests baking credentials into the image, sometimes you need runtime password changes - especially when dealing with SSH-enabled containers.
The common SSH approach:
sshpass -p 'OLDPASS' ssh root@container-IP 'echo -e "NEWPASS\\nNEWPASS" | passwd root'

often fails because:

passwd expects interactive terminal input
SSH might not be fully configured when the command runs
Password complexity requirements may block non-interactive changes

Here are more reliable Docker-native methods:
Method 1: Using docker exec
docker exec -i container_id bash -c "echo -e 'NEWPASS\\nNEWPASS' | passwd root"

Method 2: Using chpasswd
docker exec -i container_id bash -c "echo 'root:NEWPASS' | chpasswd"

Method 3: During Container Creation
docker run -d --name my_container \
  -e ROOT_PASS="NEWPASS" \
  my_image /bin/bash -c "echo 'root:$ROOT_PASS' | chpasswd && /usr/sbin/sshd -D"

When you must handle interactive prompts:
docker exec -i container_id bash -c "expect -c 'spawn passwd root; expect \"New password:\"; send \"NEWPASS\\r\"; expect \"Retype new password:\"; send \"NEWPASS\\r\"; interact'"


Never store plaintext passwords in scripts
Use Docker secrets for production environments
Consider SSH key authentication instead of password login
Implement password rotation policies

For production, consider building images with pre-configured credentials:
FROM ubuntu
RUN echo 'root:$6$salt$hashedpass' > /etc/shadow

Use openssl to generate proper shadow entries:
openssl passwd -6 -salt xyz yourpassword