How to analyze disk usage of a Docker container

Question

I can see that Docker takes 12GB of my filesystem   2 7G     var lib docker vfs dir 2 7G     var lib docker vfs 2 8G     var lib docker devicemapper mnt 6 3G     var lib docker devicemapper devicemapper 9 1G     var lib docker devicemapper 12G      var lib docker   But  how do I know how this is distributed over the containers   I tried to attach to the containers by running  the new v1 3 command   docker exec -it  lt container name gt  bash   and then running  df -h  to analyze the disk usage  It seems to be working  but not with containers that use  volumes-from    For example  I use a data-only container for MongoDB  called  mongo-data    When I run docker run -it --volumes-from mongo-data  busybox  and then df -h inside the container  It says that the filesystem mounted on  data db  my  mongo-data  data-only container  uses 11 3G  but when I do du -h  data db  it says that it uses only 2 1G   So  how do I analyze a container volume disk usage  Or  in my case  how do I find out the  mongo-data  container size

User · Answer

Alternative to docker ps --size As  quot docker ps --size quot  produces heavy IO load on host  it is not feasable running such command every minute in a production environment  Therefore we have to do a workaround in order to get desired container size or to be more precise  the size of the RW-Layer with a low impact to systems perfomance  This approach gathers the  quot device name quot  of every container and then checks size of it using  quot df quot  command  Those  quot device names quot  are thin provisioned volumes that a mounted to   on each container  One problem still persists as this observed size also implies all the readonly-layers of underlying image  In order to address this we can simple check size of used container image and substract it from size of a device thin volume  One should note that every image layer is realized as a kind of a lvm snapshot when using device mapper  Unfortunately I wasn t able to get my rhel system to print out those snapshots layers  Otherwise we could simply collect sizes of  quot latest quot  snapshots  Would be great if someone could make things clear  However    After some tests  it seems that creation of a container always adds an overhead of approx  40MiB  tested with containers based on Image  quot httpd 2 4 46-alpine quot     docker run -d --name apache httpd 2 4 46-alpine    now get device name from docker inspect and look it up using df df -T - gt  90MB whereas  quot Virtual Size quot  from  quot docker ps --size quot  states 50MB and a very small payload of 2Bytes - gt  mysterious overhead 40MB curl download of a 100MB file within container df -T - gt  190MB whereas  quot Virtual Size quot  from  quot docker ps --size quot  states 150MB and payload of 100MB - gt  overhead 40MB  Following shell prints results  in bytes  that match results from  quot docker ps --size quot   but keep in mind mentioned overhead of 40MB  for c in    docker ps -q   do   container name   docker inspect -f  quot    Name   quot    c    sed  s      g       device n   docker inspect -f  quot    GraphDriver Data DeviceName   quot    c    sed  s   -  g      device size kib   df -T   grep   device n    awk   print  4       device size byte    1024     device size kib       image sha   docker inspect -f  quot    Image   quot    c    sed  s      g       image size byte   docker image inspect -f  quot    Size   quot    image sha      container size byte      device size byte  -   image size byte         echo my node dm device size bytes  cname   quot   container name   quot      device size byte     echo my node dm container size bytes  cname   quot   container name   quot      container size byte     echo my node dm image size bytes  cname   quot   container name   quot      image size byte     done  Further reading about device mapper  https   test-dockerrr readthedocs io en latest userguide storagedriver device-mapper-driver

User · Answer

this answer is not useful  but leaving it here since some of the comments may be   docker images will show the  virtual size   i e  how much in total including all the lower layers   So some double-counting if you have containers that share the same base image   documentation

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The volume part did not work anymore so if anyone is insterested I just change the above script a little bit   for d in  docker ps   awk   print  1     tail -n  2   do     d name  docker inspect -f    Name    d      echo                                                                 echo   d name   d  container size       sudo du -d 2 -h  var lib docker aufs   grep  docker inspect -f     Id     d      echo   d name   d  volumes       for mount in  docker inspect -f    range  Mounts      Source      Destination                                                                                                                                                               end     d   do         size  echo  mount   cut -d    -f1   sudo xargs du -d 0 -h          mnt  echo  mount   cut -d    -f2          echo   size mounted on  mnt      done done

User · Answer

Improving Maxime s anwser   docker ps --size  You ll see something like this    --------------- --------------- --------------------    CONTAINER ID    IMAGE           SIZE                                                                          6ca0cef8db8d    nginx           2B  virtual 183MB      3ab1a4d8dc5a    nginx           5B  virtual 183MB     --------------- --------------- --------------------    When starting a container  the image that the container is started from is mounted read-only  virtual   On top of that  a writable layer is mounted  in which any changes made to the container are written   So the Virtual size  183MB in the example  is used only once  regardless of how many containers are started from the same image - I can start 1 container or a thousand  no extra disk space is used  The  Size   2B in the example  is unique per container though  so the total space used on disk is   183MB   5B   2B  Be aware that the size shown does not include all disk space used for a container  Things that are not included currently are     -  volumes    -  swapping    -  checkpoints    -  disk space used for log-files generated by container  https   github com docker docker github io issues 1520 issuecomment-305179362

User · Answer

To see the file size of your containers  you can use the --size argument of docker ps   docker ps --size

User · Answer

Keep in mind that docker ps --size may be an expensive command  taking more than a few minutes to complete  The same applies to container list API requests with size 1  It s better not to run it too often   Take a look at alternatives we compiled  including the du -hs option for the docker persistent volume directory

User · Answer

You can use  docker history IMAGE ID   to see how the image size is ditributed between its various sub-components

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Posting this as an answer because my comments above got hidden   List the size of a container   du -d 2 -h  var lib docker devicemapper   grep  docker inspect -f     Id     lt container name gt     List the sizes of a container s volumes   docker inspect -f     Volumes     lt container name gt    sed  s map        sed  s        tr       n    sed  s          xargs sudo du -d 1 -h   Edit  List all running containers  sizes and volumes   for d in  docker ps -q   do     d name  docker inspect -f    Name    d      echo                                                                 echo   d name   d  container size       sudo du -d 2 -h  var lib docker devicemapper   grep  docker inspect -f     Id     d      echo   d name   d  volumes       docker inspect -f     Volumes     d   sed  s map        sed  s        tr       n    sed  s          xargs sudo du -d 1 -h done   NOTE  Change  devicemapper  according to your Docker filesystem  e g  aufs

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After 1 13 0  Docker includes a new command docker system df to show docker disk usage     docker system df TYPE            TOTAL        ACTIVE     SIZE        RECLAIMABLE Images          5            1          2 777 GB    2 647 GB  95   Containers      1            1          0 B         0B Local Volumes   4            1          3 207 GB    2 261  70     To show more detailed information on space usage     docker system df --verbose

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I use docker stats   docker ps --format    Names    --no-stream to get     CPU usage   Mem usage Total mem allocated to container  can be allocate with docker run command  Mem   Block I O Net I O

[docker] How to analyze disk usage of a Docker container

Alternative to docker ps --size

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