mirror of
https://github.com/Brandon-Rozek/website.git
synced 2024-11-26 18:13:59 -05:00
70 lines
No EOL
2.1 KiB
Markdown
70 lines
No EOL
2.1 KiB
Markdown
---
|
|
title: "Auto Purge Old Docker Images"
|
|
date: 2020-09-28T23:30:22-04:00
|
|
draft: false
|
|
tags: ["Containers"]
|
|
medium_enabled: true
|
|
---
|
|
|
|
I use [Watchtower](https://github.com/containrrr/watchtower) to automatically update the docker images I use. After leaving it for several months, I've realized that I have been storing over 100GB of old docker images. I needed a way to automatically purge old images and [Systemd Timers](https://opensource.com/article/20/7/systemd-timers) is the solution.
|
|
|
|
First it's useful to know the docker command that purges unused images that are older than 24 hours old.
|
|
|
|
```bash
|
|
docker image prune -fa --filter "until=24h"
|
|
```
|
|
|
|
Then we can create a oneshot service file that will describe its dependencies and descriptions for Systemd to manage. This file is `/etc/systemd/system/docker-purge.service`.
|
|
|
|
```yml
|
|
[Unit]
|
|
Description=Purge Docker Images Older than 24 Hours
|
|
Requires=docker.service
|
|
Wants=docker-purge.timer
|
|
|
|
[Service]
|
|
Type=oneshot
|
|
ExecStart=/usr/bin/docker image prune -fa --filter "until=24h"
|
|
|
|
[Install]
|
|
WantedBy=multi-user.target
|
|
```
|
|
|
|
Now we can create the systemd timer that will hook to this service. This is `/etc/systemd/system/docker-purge.timer`.
|
|
|
|
```yaml
|
|
[Unit]
|
|
Description=Purge Docker Images Older than 24 Hours
|
|
Requires=docker-purge.service
|
|
|
|
[Timer]
|
|
Unit=docker-purge.service
|
|
OnCalendar=*-*-* 00:00:00
|
|
AccuracySec=24h
|
|
|
|
[Install]
|
|
WantedBy=timers.target
|
|
```
|
|
|
|
This tells Systemd to run the service every day if enabled/started, though not necessarily at midnight. Systemd will schedule a time to run the service within the `AccuracySec` parameter. That is, it will schedule a time to run sometime everyday.
|
|
|
|
Finally, let's enable and start the timer.
|
|
|
|
```bash
|
|
sudo systemctl enable docker-purge
|
|
sudo systemctl start docker-purge
|
|
```
|
|
|
|
We can check the time that docker-purge is scheduled to run next by asking Systemd to list its timers.
|
|
|
|
```bash
|
|
systemctl list-timers
|
|
```
|
|
|
|
If you want to play around with the `OnCalendar` parameter. A useful command is
|
|
|
|
```bash
|
|
systmed-analyze calendar --iterations=$N "$TIME"
|
|
```
|
|
|
|
Where you replace `$N` with an integer, and `$TIME` with your sample time string. |