There is a wonderfully easy way to install cdo, which takes care of all the libraries for you, and you can do it within your user directory, so don’t need special privileges: use conda!
conda config --add channels conda-forge conda update --all conda install cdo cdo
This cdo seems to work happily with GRIB and NetCDF data, and also installs lots of other useful tools, in particular
To convert IFS from GRIB to NetCDF, I think the best command to use may be:
grib_to_netcdf -T /pithos/shared/ESIPP/ECMWF/IFS/IFS_IT00_20180101_20180107.grib -o IFS.cdf
The “-T” option is good here, as it converts the data using the dimensions:
longitude = 80 ; latitude = 58 ; step = 49 ; date = 7 ;
where date is when the forecast started (initialisation time, IT), and step is the forecast time (0 to 48).