Container Universe Jobs
In addition to Docker, many competing container runtimes have been developed, some of which are mostly compatible with Docker, and others which provide their own feature sets. Many HTCondor users and administrators want to run jobs inside containers, but don’t care which runtime is used.
HTCondor’s container universe provides an abstraction where the user does not specify exactly which container runtime to use, but just aspects of their contained job, and HTCondor will select an appropriate runtime. To do this, set the job submit file command container_image to a specified container image.
Note that the container may specify the executable to run, either in the runfile option of a singularity image, or in the entrypoint option of a Dockerfile. If this is set, the executable command in the HTCondor submit file is optional, and the default command in the container will be run.
This container image may describe an image in a docker-style repo if it
is prefixed with
docker://, or a Singularity
.sif image on disk, or a
Singularity sandbox image (an exploded directory). condor_submit
will parse this image and advertise what type of container image it
is, and match with startds that can support that image.
The container image may also be specified with an URL syntax that tells HTCondor to use a file transfer plugin to transfer the image. For example with
container_image = http://example.com/dir/image.sif
A container image that would otherwise be transferred can be forced to never be transferred by setting
should_transfer_container = no
HTCondor knows that “docker://” and “oras://” (for apptainer) are special, and are never transferred by HTCondor plugins.
Here is a complete submit description file for a sample container universe job:
#universe = container is optional
universe = container
container_image = ./image.sif
executable = /bin/cat
arguments = /etc/hosts
should_transfer_files = YES
when_to_transfer_output = ON_EXIT
output = out.$(Process)
error = err.$(Process)
log = log.$(Process)
request_cpus = 1
request_memory = 1024M
request_disk = 10240K