Our server was running out of disk space due to some docker diff files piling up (it seems they need to be cleaned out regularly, but that is a different topic). After making some space, ps:rebuild is not working anymore, it just returns immediately with no output. And we can also not push anymore to the server, we get:

! [remote rejected]   dokku -> master (pre-receive hook declined)
error: failed to push some refs to 'dokku@.....:.....'

Help is greatly appreciated.

dokku report
-----> uname: Linux ubuntu-512mb-fra1-01 3.13.0-77-generic #121-Ubuntu SMP Wed Jan 20 10:50:42 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
-----> memory:
total used free shared buffers cached
Mem: 994 647 346 10 19 111
-/+ buffers/cache: 515 478
Swap: 999 112 887
-----> docker version:
Client:
Version: 17.05.0-ce
API version: 1.29
Go version: go1.7.5
Git commit: 89658be
Built: Thu May 4 22:06:06 2017
OS/Arch: linux/amd64

Server:
Version: 17.05.0-ce
API version: 1.29 (minimum version 1.12)
Go version: go1.7.5
Git commit: 89658be
Built: Thu May 4 22:06:06 2017
OS/Arch: linux/amd64
Experimental: false
-----> docker daemon info:
Containers: 12
Running: 5
Paused: 0
Stopped: 7
Images: 32
Server Version: 17.05.0-ce
Storage Driver: aufs
Root Dir: /var/lib/docker/aufs
Backing Filesystem: extfs
Dirs: 1133
Dirperm1 Supported: false
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host macvlan null overlay
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 9048e5e50717ea4497b757314bad98ea3763c145
runc version: 9c2d8d184e5da67c95d601382adf14862e4f2228
init version: 949e6fa
Security Options:
apparmor
Kernel Version: 3.13.0-77-generic
Operating System: Ubuntu 14.04.5 LTS
OSType: linux
Architecture: x86_64
CPUs: 1
Total Memory: 994MiB
Name: ubuntu-512mb-fra1-01
ID: 5XQF:UC63:3ZUV:GI2Y:JEWP:NJHA:NQ6X:5IKC:RRFA:XLTA:IILX:HBUZ
Docker Root Dir: /var/lib/docker
Debug Mode (client): true
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Experimental: false
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false

WARNING: No swap limit support
-----> sigil version: 0.4.0
-----> herokuish version:
herokuish: 0.3.31
buildpacks:
heroku-buildpack-multi v1.0.0
heroku-buildpack-ruby v163
heroku-buildpack-nodejs v99
heroku-buildpack-clojure v76
heroku-buildpack-python v109
heroku-buildpack-java v52
heroku-buildpack-gradle v22
heroku-buildpack-grails v21
heroku-buildpack-scala v76
heroku-buildpack-play v26
heroku-buildpack-php v121
heroku-buildpack-go v69
heroku-buildpack-erlang fa17af9
buildpack-nginx v8
-----> dokku version: 0.5.7
-----> dokku plugins:
plugn: 0.3.0
00_dokku-standard 0.5.7 enabled dokku core standard plugin
20_events 0.5.7 enabled dokku core events logging plugin
apps 0.5.7 enabled dokku core apps plugin
build-env 0.5.7 enabled dokku core build-env plugin
certs 0.5.7 enabled dokku core certificate management plugin
checks 0.5.7 enabled dokku core checks plugin
common 0.5.7 enabled dokku core common plugin
config 0.5.7 enabled dokku core config plugin
docker-options 0.5.7 enabled dokku core docker-options plugin
domains 0.5.7 enabled dokku core domains plugin
enter 0.5.7 enabled dokku core enter plugin
git 0.5.7 enabled dokku core git plugin
letsencrypt 0.8.6 enabled Automated installation of let's encrypt TLS certificates
logs 0.5.7 enabled dokku core logs plugin
memcached 1.0.0 enabled dokku memcached service plugin
named-containers 0.5.7 enabled dokku core named containers plugin
nginx-vhosts 0.5.7 enabled dokku core nginx-vhosts plugin
plugin 0.5.7 enabled dokku core plugin plugin
postgres 1.0.0 enabled dokku postgres service plugin
proxy 0.5.7 enabled dokku core proxy plugin
ps 0.5.7 enabled dokku core ps plugin
shell 0.5.7 enabled dokku core shell plugin
storage 0.5.7 enabled dokku core storage plugin
tags 0.5.7 enabled dokku core tags plugin
tar 0.5.7 enabled dokku core tar plugin

Environment details (AWS, VirtualBox, physical, etc.): Digital Ocean