How to correctly run long-running shell commands when you are doing DB migrations

When running long-running shell commands, such as database migrations, over an SSH connection, it’s important to ensure the process continues even if your SSH session is interrupted. There are a few strategies you can use:

Using nohup (No Hang Up):

• nohup allows a command to keep running after the session is closed.
• Usage:

nohup <your-command> &

• Example for a database migration:

nohup python manage.py migrate &

• This will redirect the command’s output to a file named nohup.out in the current directory.

Using screen:

• screen allows you to start a command and then disconnect, leaving the command running in the background.
• Start a new screen session:
• screen
• Run your command inside the screen session:

python manage.py migrate

• Detach from the screen session by pressing Ctrl-A followed by D.
• You can reattach to the session later using:
• screen -r

Using tmux:

• tmux is similar to screen and is used for managing multiple terminal sessions.
• Start a new tmux session:

tmux

• Run your command inside the tmux session:

python manage.py migrate

• Detach from the tmux session by pressing Ctrl-B followed by D.
• You can reattach to the session later using:
• tmux attach

Using disown:

• disown can be used to remove jobs from the shell's job table, allowing them to continue running after the shell session ends.
• Run your command in the background:

python manage.py migrate &

• Get the job ID of the command using jobs:

jobs

• Use disown with the job ID:

disown %1

These methods ensure that your database migrations or any other long-running commands continue to execute even if your SSH session is disconnected.