Docker error invalid reference format repository name must be lowercase

Question

Ran into this Docker error with one of my projects   invalid reference format  repository name must be lowercase  What are the various causes for this generic message   I already figured it out after some effort  so I m going to answer my own question in order to document it here as the solution doesn t come up right away when doing a web search and also because this error message doesn t describe the direct problem Docker encounters

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For me the issue was with the space in volume mapping that was not escaped  The jenkins job which was running the docker run command had a space in it and as a result docker engine was not able to understand the docker run command

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On MacOS when your are working on an iCloud drive  your  PWD will contain a directory  Mobile Documents   It does not seem to like the space   As a workaround  I copied my project to local drive where there is no space in the  path to my project folder   I do not see a way you can get around changnig the default path to iCloud which is   Library Mobile Documents com apple CloudDocs  The space in the path in  Mobile Documents  seems to be what docker run does not like

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In my case the problem was in parameters arrangement  Initially I had --name parameter after environment parameters and then volume and attach dbs  parameters  and image at the end of command like below    docker run -p 1433 1433 -e sa password myComplexPwd -e ACCEPT EULA Y --name sql1 -v c  temp  c  temp  attach dbs     dbName   TestDb   dbFiles    c   temp  TestDb mdf   c   temp  TestDb log ldf      -d microsoft mssql-server-windows-express   After rearranging the parameters like below everything worked fine  basically putting --name parameter followed by image name    docker run -d -p 1433 1433 -e sa password myComplexPwd -e ACCEPT EULA Y --name sql1 microsoft mssql-server-windows-express -v C  temp  C  temp  attach dbs     dbName   TestDb   dbFiles    C   temp  TestDb mdf   C   temp  TestDb log ldf

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A reference in Docker is what points to an image  This could be in a remote registry or the local registry  Let me describe the error message first and then show the solutions for this      invalid reference format   This means that the reference we have used is not a valid format  This means  the reference  pointer  we have used to identify an image is invalid  Generally  this is followed by a description as follows  This will make the error much clearer      invalid reference format  repository name must be lowercase   This means the reference we are using should not have uppercase letters  Try running docker run Ubuntu  wrong  vs docker run ubuntu  correct   Docker does not allow any uppercase characters as an image reference  Simple troubleshooting steps   1  Dockerfile contains a capital letters as images    FROM Ubuntu  wrong  FROM ubuntu  correct    2  Image name defined in the docker-compose yml had uppercase letters  3  If you are using Jenkins or GoCD for deploying your docker container  please check the run command  whether the image name includes a capital letter   Please read this document written specifically for this error

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In my case  the image name defined in docker-compose yml contained uppercase letters  The fact that the error message mentioned repository instead of image did not help describe the problem and it took a while to figure out

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Let me emphasise that Docker doesn t even allow mixed characters   Good       docker build -t myfirstechoimage 0 1    Bad      docker build -t myFirstEchoImage 0 1

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docker build -f Dockerfile -t SpringBoot-Docker    As in the above commend  we are creating an image file for docker container  commend says create image use file -f refer to docker file  and -t for the target of the image file we are going to push to docker  the     represents the current directory   solution for the above problem  provide target image name in lowercase

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Indeed  the docker registry as of today  sha 2e2f252f3c88679f1207d87d57c07af6819a1a17e22573bcef32804122d2f305  does not handle paths containing upper-case characters  This is obviously a poor design choice  probably due to wanting to maintain compatible with certain operating systems that do not distinguish case at the file level  ie  windows     If one authenticates for a scope and tries to fetch a non-existing repository with all lowercase  the output is    auth step not shown  curl -s -H  Authorization  Bearer  TOKEN  -X GET https    LOCALREGISTRY v2 test someproject tags list   errors     code   UNAUTHORIZED   message   authentication required   detail     Type   repository   Class      Name   test someproject   Action   pull         However  if one tries to do this with an uppercase component  only 404 is returned    authorization step done but not shown here    curl -s -H  Authorization  Bearer  TOKEN  -X GET https   docker uibk ac at 443 v2 test Someproject tags list  404 page not found

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I had the same error  and for some reason it appears to have been cause by uppercase letters in the Jenkins job that ran the docker run command

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Replacing image    DOCKER REGISTRY notificationsapi  with image notificationsapi  or     image    docker registry notificationsapi in docker-compose yml did solves the issue  file with error    version   3 4   services    notifications api      image    DOCKER REGISTRY notificationsapi     build        context          dockerfile     Notifications Api Dockerfile   file without error   version   3 4   services   notifications api      image    docker registry notificationsapi     build        context          dockerfile     Notifications Api Dockerfile   So i think error was due to non lower case letters it had

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In my case DockerFile contained the image name in mixed case instead of lower case    Earlier line in my DockerFile  FROM CentOs   and when I changed above to FROM centos  it worked smoothly

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A  reference  in docker is a pointer to an image  It may be an image name  an image ID  include a registry server in the name  use a sha256 tag to pin the image  and anything else that can be used to point to the image you want to run   The invalid reference format error message means docker cannot convert the string you ve provided to an image  This may be an invalid name  or it may be from a parsing error earlier in the docker run command line if that s how you run the image  With a compose file  if you expand a variable in the image name  that variable may not be expanding correctly   With the docker run command line  this is often the result in not quoting parameters with spaces  and mistaking the order of the command line  The command line is ordered as   docker   args to docker  run   args to run  image ref   cmd to exec    The most common error in passing args to the run is a volume mapping expanding a path name that includes a space in it  and not quoting the path or escaping the space  E g   docker run -v   pwd   data image ref   And the fix is as easy as   docker run -v    pwd   data  image ref

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In my case was the -e before the parameters for mysql docker  docker run --name mysql-standalone -e MYSQL ROOT PASSWORD hello -e MYSQL DATABASE hello -e MYSQL USER hello -e MYSQL PASSWORD hello -d mysql 5 6   Check also if there are missing whitespaces

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In my case I was trying to run postgres through docker  Initially I was running as     docker run -d -p 5432 5432 -e POSTGRES PASSWORD test password POSTGRES USER test user POSTGRES DB test db --rm -v   docker volumes postgres  var lib postgresql data --name pg-docker postgres  I was missing -e after each environment variable  Changing the above command to the one below worked  docker run -d -p 5432 5432 -e POSTGRES PASSWORD test password -e POSTGRES USER test user -e POSTGRES DB test db --rm -v   docker volumes postgres  var lib postgresql data --name pg-docker postgres

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This is happening because of the spaces in the current working directory that came from   pwd  for map volumes  So  I used docker-compose instead   The docker-compose yml file   version   3  services    react-app      build        context          dockerfile  Dockerfile dev     ports        -  3000 3000      volumes        -  app node modules       -    app

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I wish the error message would output the problem string  I was getting this due to a weird copy and paste problem of a  docker run  command  A space-like character was being used before the repo and image name

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had a space in the current working directory and usign   pwd  to map volumes  Doesn t like spaces in directory names

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Most of the answers above did not work for my case  so I will document this in case somebody finds it helpful  The first line in the dockerfile FROM node 10 for my case  the word node should not be uppercase i e FROM NODE 10  I made that change and it worked

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In my case I had a naked --env switch  i e  one without an actual variable name or value  e g    docker run      --env          lt ----- This was the offending item    --rm      --volume   home shared  shared     docker build   -q

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Docker can build images automatically by reading the instructions from a Dockerfile  A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image   example      FROM python 3 7-alpine The  python  should be in lowercase

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sometimes you miss -e flag while specific multiple env vars inline  e g  bad  docker run --name somecontainername -e ENV VAR1 somevalue1 ENV VAR2 somevalue2 -d -v  mypath containerpath   lt imagename e g  postgres gt   good  docker run --name somecontainername -e ENV VAR1 somevalue1 -e ENV VAR2 somevalue2 -d -v  mypath containerpath   lt imagename e g  postgres gt

[docker] Docker error: invalid reference format: repository name must be lowercase

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