Allow arbitrary --user values

[tianon]

Closes#53 (carried)

This is implemented in the same way we've supported arbitrary values for docker run --user in many other images.

See also docker-library/rabbitmq#60, docker-library/cassandra#48, docker-library/mongo#81, redis/docker-library-redis#48, docker-library/mysql#161, and MariaDB/mariadb-docker#59, docker-library/percona#21.

[tianon]

$ docker run -it --rm --user "$RANDOM:$RANDOM" --name ghost c0704a28c3d5npm info it worked if it ends with oknpm info using npm@2.15.11npm info using node@v4.7.0npm info prestart ghost@0.11.3npm info start ghost@0.11.3
> ghost@0.11.3 start /usr/src/ghost
> node indexWARNING: Ghost is attempting to use a direct method to send email. It is recommended that you explicitly configure an email service.Help and documentation can be found at http://support.ghost.org/mail.Migrations: Creating tables...Migrations: Creating table: postsMigrations: Creating table: usersMigrations: Creating table: rolesMigrations: Creating table: roles_usersMigrations: Creating table: permissionsMigrations: Creating table: permissions_usersMigrations: Creating table: permissions_rolesMigrations: Creating table: permissions_appsMigrations: Creating table: settingsMigrations: Creating table: tagsMigrations: Creating table: posts_tagsMigrations: Creating table: appsMigrations: Creating table: app_settingsMigrations: Creating table: app_fieldsMigrations: Creating table: clientsMigrations: Creating table: client_trusted_domainsMigrations: Creating table: accesstokensMigrations: Creating table: refreshtokensMigrations: Creating table: subscribersMigrations: Running fixture populationsMigrations: Creating ownerGhost is running in development... Listening on 0.0.0.0:2368 Url configured as: http://localhost:2368 Ctrl+C to shut down

$ docker top ghostUID PID PPID C STIME TTY TIME CMD27628 25665 25650 3 15:10 pts/8 00:00:00 npm27628 25902 25665 0 15:10 pts/8 00:00:00 sh -c node index27628 25903 25902 23 15:10 pts/8 00:00:04 node index

[tianon]

Ok, this is weird:

$ docker run -it --rm --name ghost c0704a28c3d5ln: failed to create symbolic link '/usr/src/ghost/config.js': Permission denied

(running it as root, thus getting the gosu behavior rather than simply running as a different user)

Not sure yet why that'd cause any difference at all.

[ghost]

May I suggest an update of the documentation to reflect this possibility?
And how do we set the '--user' when using docker-compose?

[yosifkit]

docker-compose would just be user: 1000 or user: 999:50, so it uses the same single string as --user.

[tianon]

Ok, this is updated now. 👍

(Creating the symlink at build-time instead of run-time.)