where is logs file kept in docker container and how to copy it?

Question

i have a dockerfile like this.

when i docker compose up the service, i can use command to view logs.

docker test -f logs

i want to copy the logs file to my local machine.

where is the path?

docker file

FROM mcr.microsoft.com/dotnet/core/sdk:3.1-alpine AS build-env
WORKDIR /app

# Copy everything else and build
COPY ./ /app/
RUN dotnet restore -r linux-musl-x64 -s http://nexus.thedevcloud.net/repository/nuget-group/
RUN dotnet publish -r linux-musl-x64 -c Release -o DrugSync/out --no-restore

# Build runtime image
FROM mcr.microsoft.com/dotnet/core/aspnet:3.1-alpine

RUN apk add --no-cache icu-libs
ENV DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=false 
ENV LC_ALL=en_US.UTF-8 
ENV LANG=en_US.UTF-8 

WORKDIR /app
COPY --from=build-env /app/test/out/ /app/
ENTRYPOINT ["/app/test"]

score 2 · Answer 1 · edited Dec 31 '21 at 08:57

2

Log files can be found at:

/var/lib/docker/containers/<container id>/<container id>-xxx.log

Where xxx stands for different formats based on how you have configured it.

You can docker inspect each container to see where their logs are:

docker inspect --format='{{.LogPath}}' $INSTANCE_ID

More details about configuring logging is here

EDIT:

Similar question here
Also I tried it on mine at it shows up:

$ docker inspect --format='{{.LogPath}}' 878eb2faac5c

/var/lib/docker/containers/878eb2faac5c9fe743fd9e9e6ba6ff7e0c3f1e02964df77e5a788dcd985c0d0b/878eb2faac5c9fe743fd9e9e6ba6ff7e0c3f1e02964df77e5a788dcd985c0d0b-json.log

Note:

On Mac machines this location would be on the VM hosting the docker containers and not on the MacOS Host.

Try screen ~/Library/Containers/com.docker.docker/Data/vms/0/tty to access the location.

edited Dec 31 '21 at 08:57

J. Scott Elblein

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answered Feb 26 '20 at 07:00

John Eipe

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i did not find /var/lib/docker folder. inside /var/lib no docker folder. anything i missed in docker file? – user2201789 Feb 26 '20 at 07:01
i am using docker desktop windows , linux container at windows 10. i did not see instance id when i docker ps – user2201789 Feb 26 '20 at 07:04
use docker ps -a – John Eipe Feb 26 '20 at 07:05
did u mean container id? – user2201789 Feb 26 '20 at 07:05
docker inspect --format='{{.LogPath}}' af3f1ad82cde '/var/lib/docker/containers/af3f1ad82cdeea41756fc62897c7b734d17b2fbc75749174283a6db9024d756b/af3f1ad82cdeea41756fc62897c7b734d17b2fbc75749174283a6db9024d756b-json.log' – user2201789 Feb 26 '20 at 07:06
how do i navigate to the path? i used docker exec -it test /bin/sh – user2201789 Feb 26 '20 at 07:07
First get the container id using `$docker ps -a` then `$docker inspect --format='{{.LogPath}}' your_continerid` – John Eipe Feb 26 '20 at 07:07
docker exec -it test /bin/sh . then cd .. then cd var/lib , there is no docker folder – user2201789 Feb 26 '20 at 07:07
yes i got the long string-json.log but i cannot navigate to that path...i just want to copy it out to my machine – user2201789 Feb 26 '20 at 07:10
i think it might be a problem with non-linux machines. Maybe try to pipe the `docker logs your_containerid` into some file – John Eipe Feb 26 '20 at 07:11
On Mac and Windows, it uses VM to run the docker containers so the location might be not on the base machine but on the VM. To access it: https://stackoverflow.com/questions/48180981/docker-container-log-file-not-found-on-mac – John Eipe Feb 26 '20 at 07:17
okay that is for mac...any idea how to do it at windows? or any tool? – user2201789 Feb 26 '20 at 07:26
Try this: https://nickjanetakis.com/blog/docker-tip-70-gain-access-to-the-mobylinux-vm-on-windows-or-macos – John Eipe Feb 26 '20 at 07:31
no luck / # du -chs /var/lib/docker/containers/*/*json.log du: /var/lib/docker/containers/*/*json.log: No such file or directory 0 total – user2201789 Feb 26 '20 at 09:43
does the path `/var/lib/docker/containers/`at least exist now? – John Eipe Feb 27 '20 at 05:29
nope. as i mentioned earlier, the problem is i cannot find the relevant path – user2201789 Feb 27 '20 at 06:16

where is logs file kept in docker container and how to copy it?

1 Answers1