How to Create Temp Directory Auto-Delete on Ubuntu Reboot

This article details the process of setting up a custom temporary directory in Ubuntu that automatically purges its contents during system startup. You will learn how to utilize systemd-tmpfiles to define cleanup rules, ensuring reliable management of temporary data without manual intervention or complex scripts.

Use Built-in Temporary Locations

The simplest method is to use the existing /tmp or /run directories. Both locations are cleared automatically every time the system boots. If your application allows it, store temporary files directly in /tmp to leverage this built-in behavior without additional configuration.

Create a Custom Temporary Directory

If you require a specific path, such as /var/myapp/temp, you must configure systemd to manage it. Ubuntu uses systemd-tmpfiles to handle the creation and cleaning of temporary directories.

1. Create a Configuration File

Create a new configuration file in the /etc/tmpfiles.d/ directory. This tells systemd how to handle your specific folder. Replace myapp with your desired service name.

sudo nano /etc/tmpfiles.d/myapp.conf

2. Define the Cleanup Rule

Add the following line to the file. This command specifies that the directory should be created with specific permissions and removed during boot.

d /var/myapp/temp 0755 root root -

• d: Creates the directory if it does not exist.
• /var/myapp/temp: The path to your temporary directory.
• 0755: Permissions for the directory.
• root root: User and group ownership.
• -: Age argument. Using - means the directory itself persists, but you can add a time value (e.g., 1d) to delete files older than one day. To ensure the content is wiped on reboot, systemd typically clears directories defined here depending on the specific setup, but for a strict reboot wipe, rely on the next step.

For a strict reboot-only wipe of content, use the L or d type combined with systemd boot services. However, the most reliable method for a full wipe on boot is to mount a tmpfs or rely on the systemd-tmpfiles-clean.service which runs at boot.

To ensure the directory is emptied on boot, add this line instead:

D /var/myapp/temp 0755 root root -

The capital D argument creates the directory and removes its contents if it already exists when the systemd-tmpfiles-setup service runs during boot.

3. Apply the Configuration

Create the directory immediately and test the configuration without rebooting by running:

sudo systemd-tmpfiles --create /etc/tmpfiles.d/myapp.conf

4. Verify the Setup

Reboot your system to confirm the behavior.

sudo reboot

After the system restarts, check the directory. It should exist but be empty.

ls -la /var/myapp/temp

Any files created before the reboot will be gone, ensuring a clean state for your applications.