How to redirect docker container logs to a single file

Question

I want to redirect all the logs of my docker container to single log file to analyse them  I tried   docker logs container  gt   tmp stdout log 2 gt  tmp stderr log   but this gives log in two different file  I already tried   docker logs container  gt   tmp stdout log   but it did not work

User · Accepted Answer

No need to redirect logs   Docker by default store logs to one log file  To check log file path run command   docker inspect --format     LogPath    containername   var lib docker containers f844a7b45ca5a9589ffaa1a5bd8dea0f4e79f0e2ff639c1d010d96afb4b53334 f844a7b45ca5a9589ffaa1a5bd8dea0f4e79f0e2ff639c1d010d96afb4b53334-json log   Open that log file and analyse   if you redirect logs then you will only get logs before redirection  you will not be able to see live logs   EDIT   To see live logs you can run below command  tail -f  docker inspect --format     LogPath    containername    Note    This log file  var lib docker containers f844a7b45ca5a9589ffaa1a5bd8dea0f4e79f0e2ff639c1d010d96afb4b53334 f844a7b45ca5a9589ffaa1a5bd8dea0f4e79f0e2ff639c1d010d96afb4b53334-json log will be created only if docker generating logs if there is no logs then this file will not be there  it is similar like sometime if we run command docker logs containername and  it returns nothing  In that scenario this file will not be available

User · Answer

To capture both stdout  amp  stderr from your docker container to a single log file run the following   docker logs container  gt  container log 2 gt  amp 1

User · Answer

Assuming that you have multiple containers and you want to aggregate the logs into a single file  you need to use some log aggregator like fluentd  fluentd is supported as logging driver for docker containers   So in docker-compose  you need to define the logging driver    service1      image  webapp 0 0 1     logging        driver   fluentd        options          tag  service1     service2          image  myapp 0 0 1         logging            driver   fluentd            options              tag  service2   The second step would be update the fluentd conf to cater the logs for both service 1 and service 2    lt match service1 gt      type copy     lt store gt       type file     path  fluentd log service service   log     time slice format  Y m d     time slice wait 10m     time format  Y m dT H M S z    lt  store gt    lt  match gt     lt match service2 gt       type copy     lt store gt       type file     path  fluentd log service service   log     time slice format  Y m d     time slice wait 10m     time format  Y m dT H M S     lt  store gt    lt  match gt     In this config  we are asking logs to be written to a single file to this path  fluentd log service service   log  and the third step would be to run the customized fluentd which will start writing the logs to file   Here is the link for step by step instructions  Bit Long  but correct way since you get more control over log files path etc and it works well in Docker Swarm too

User · Answer

First check your container id   docker ps -a   You can see first row in CONTAINER ID columns  Probably it looks like this  3fd0bfce2806  then type it in shell  docker inspect --format     LogPath    3fd0bfce2806   You will see something like this    var lib docker containers 3fd0bfce2806b3f20c2f5aeea2b70e8a7cff791a9be80f43cdf045c83373b1f1 3fd0bfce2806b3f20c2f5aeea2b70e8a7cff791a9be80f43cdf045c83373b1f1-json log   then you can see it as   cat  var lib docker containers 3fd0bfce2806b3f20c2f5aeea2b70e8a7cff791a9be80f43cdf045c83373b1f1 3fd0bfce2806b3f20c2f5aeea2b70e8a7cff791a9be80f43cdf045c83373b1f1-json log   It would be in JSON format  you can use the timestamp to trace errors

User · Answer

docker logs -f docker container name  gt  gt  YOUR LOG PATH 2 gt  amp 1  amp

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docker logs -f  lt yourContainer gt   amp  gt  your log  amp   Explanation    -f  i e --follow   writes all existing logs and continues  follows  logging everything that comes next   amp  gt  redirects both the standard output and standard error  Likely you want to run that method in the background  thus the  amp   You can separate output and stderr by   gt  output log 2 gt  error log  instead of using  amp  gt

User · Answer

If you work on Windows and use PowerShell  like me   you could use the following line to capture the stdout and stderr    docker logs  lt containerId gt    Out-File  C  dev mylog txt    I hope it helps someone

User · Answer

How about this option   docker logs containername  gt  amp  logs myFile log  It will not redirect logs which was asked for in the question  but copy them once to a specific file

User · Answer

The easiest way that I use is this command on terminal   docker logs elk  gt   home Desktop output log   structure is   docker logs  lt Container Name gt   gt  path filename log

User · Answer

Bash script to copy all container logs to a specified directory      usr bin env bash  TARGET DIR   logs docker logs mkdir -p   TARGET DIR  for name in  sudo docker ps --format     Names      do     path   sudo docker inspect --format     LogPath     name      sudo cp -rf   path    TARGET DIR   name log done

User · Answer

Since Docker merges stdout and stderr for us  we can treat the log output like any other shell stream  To redirect the current logs to a file  use a redirection operator    docker logs test container  gt  output log   docker logs -f test container  gt  output log  Instead of sending output to stderr and stdout  redirect your application   s output to a file and map the file to permanent storage outside of the container     docker logs test container gt   tmp output log   Docker will not accept relative paths on the command line  so if you want to use a different directory  you   ll need to use the complete path

[logging] How to redirect docker container logs to a single file?

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