Docker-Gen Cannot Generate Configuration

[maxexcloo]

When the output file is set to be written to a volume, docker-gen is unable to create the configuration there due to what appears to be a hard link error.

[maxexcloo]

Example is in my HAProxy Configuration Generator container and the HAProxy container itself:

HAProxy Config
https://github.com/maxexcloo/Docker/tree/master/apps/haproxy-config
docker run --name="haproxy-config" -v /var/run/docker.sock:/tmp/docker.sock -i -t maxexcloo/haproxy-config

HAProxy
https://github.com/maxexcloo/Docker/tree/master/apps/haproxy
docker run --name="haproxy" --volumes-from="haproxy-config" -p 80:80 -p 443:443 -i -t maxexcloo/haprox

[jwilder]

I'm not sure what's happening. I tried your containers but but wasn't quite sure how to use them. I'll see if I can reproduce using --volumes-from. If you have some steps that I can follow to reproduce the error that would be helpful.

[maxexcloo]

Basically if the generated template output path is on an external volume there is a copy error, I believe due to how linux handles hardlinks.

[smirolo]

I seem to have the same (or related) issue:

$ ./docker-gen -only-exposed -watch -notify "/etc/init.d/nginx reload"     nginx.tmpl /etc/nginx/conf.d/default.conf
2014/06/14 11:17:35 unable to create dest file /etc/nginx/conf.d/default.conf: rename /tmp/docker-gen598781669 /etc/nginx/conf.d/default.conf: invalid cross-device link

$ df
Filesystem              1K-blocks    Used Available Use% Mounted on
/dev/mapper/fedora-root  17938864 3173340  13831228  19% /
tmpfs                      505400      44    505356   1% /tmp

Most likely because docker-gen tries to do a file rename instead of a file copy.

#https://github.com/jwilder/docker-gen/blob/master/template.go#L106
err = os.Rename(dest.Name(), config.Dest)

I managed to workaround the problem by explicitly overriding the TMPDIR shell variable as such (for example):

TMPDIR=/etc/nginx/tmp ./docker-gen -only-exposed -watch -notify "/etc/init.d/nginx reload" nginx.tmpl /etc/nginx/conf.d/default.conf

[quokkamole]

"Unable to create dest file /etc/nginx/conf.d/default.conf: rename /etc/nginx/conf.d/docker-gen"

I got this problem when launching (via docker-compose) from a shared folder on a windows host (linux guest in virtualbox) presumably due to associated file manipulation limitations as outlined above. Solution: run on the guest fs.