"ps" command not in singularity container

@rgracia and I tried to add a process to the neutrino simulation nextflow pipeline that executes the h5extract/h5extractf command on the root files produced in the previous steps of the pipeline. For this, the singularity container /home/saturn/capn/mppi104h/singularity/km3pipe_v9.8.0 was used. The process terminates with the error message Command 'ps' required by nextflow to collect task metrics cannot be found. Is it possible to add that command to the container?