How to clear the logs properly for a Docker container?

Question

I use docker logs [container-name] to see the logs of a specific container.

Is there an elegant way to clear these logs?

Answer 1

On my Ubuntu servers even as sudo I would get Cannot open ‘/var/lib/docker/containers/*/*-json.log’ for writing: No such file or directory

But combing the docker inspect and truncate answers worked :

sudo truncate -s 0 `docker inspect --format='{{.LogPath}}' <container>`

Answer 2

As a root user, try to run the following:

>  /var/lib/docker/containers/*/*-json.log

or

cat /dev/null > /var/lib/docker/containers/*/*-json.log

or

echo "" > /var/lib/docker/containers/*/*-json.log

Answer 3

Docker for Mac users, here is the solution:

• 1. Find log file path by:

     $ docker inspect | grep log

• 2. SSH into the docker machine( suppose the name is default, if not, run docker-machine ls to find out):

     $ docker-machine ssh default

• 3. Change to root user(reference):

     $ sudo -i

• 4. Delete the log file content:

     $ echo "" > log_file_path_from_step1

Answer 4

Docker4Mac, a 2018 solution:

LOGPATH=$(docker inspect --format='{{.LogPath}}' <container_name_or_id>)
docker run -it --rm --privileged --pid=host alpine:latest nsenter -t 1 -m -u -n -i -- truncate -s0 $LOGPATH

The first line gets the log file path, similar to the accepted answer.

The second line uses nsenter that allows you to run commands in the xhyve VM that servers as the host for all the docker containers under Docker4Mac. The command we run is the familiar truncate -s0 $LOGPATH from non-Mac answers.

If you're using docker-compose, the first line becomes:

local LOGPATH=$(docker inspect --format='{{.LogPath}}' $(docker-compose ps -q <service>))

and <service> is the service name from your docker-compose.yml file.

Thanks to https://github.com/justincormack/nsenter1 for the nsenter trick.

Answer 5

I needed something I could run as one command, instead of having to write docker ps and copying over each Container ID and running the command multiple times. I've adapted BMitch's answer and thought I'd share in case someone else may find this useful.

Mixing xargs seems to pull off what I need here:

docker ps --format='{{.ID}}' | \
  xargs -I {} sh -c 'echo > $(docker inspect --format="{{.LogPath}}" {})'

This grabs each Container ID listed by docker ps (will erase your logs for any container on that list!), pipes it into xargs and then echoes a blank string to replace the log path of the container.

Answer 6

You can set up logrotate to clear the logs periodically.

Example file in /etc/logrotate.d/docker-logs

/var/lib/docker/containers/*/*.log {
 rotate 7
 daily
 compress
 size=50M
 missingok
 delaycompress
 copytruncate
}