Looks like Solus misses a clean-up mechanism for old modules under /lib64/modules.
This machine was installed a year ago (Solus 2017.01.01 ISO)
py@solus-laptop /lib64/modules $ ls /lib64/modules 4.14.8-41.current 4.9.23-21.lts 4.9.38-34.lts 4.9.51-48.lts 4.9.64-59.lts 4.14.9-42.current 4.9.24-22.lts 4.9.39-35.lts 4.9.53-51.lts 4.9.65-60.lts 4.8.15 4.9.25-24.lts 4.9.41-37.lts 4.9.56-52.lts 4.9.66-61.lts 4.9.12 4.9.26-25.lts 4.9.43-39.lts 4.9.57-53.lts 4.9.67-62.lts 4.9.13 4.9.27-27.lts 4.9.44-41.lts 4.9.59-55.lts 4.9.68-63.lts 4.9.16 4.9.29-28.lts 4.9.45-42.lts 4.9.6 4.9.69-64.lts 4.9.18-10.lts 4.9.30-29.lts 4.9.46-43.lts 4.9.60-56.lts 4.9.7 4.9.20-12.lts 4.9.32-30.lts 4.9.49-46.lts 4.9.61-57.lts 4.9.71-65.lts 4.9.22-17.lts 4.9.32-31.lts 4.9.51-47.lts 4.9.62-58.lts 4.9.72-66.lts py@solus-laptop /lib64/modules $ du -sh /lib64/modules 4,4G /lib64/modules
This machine was installed a month ago
py ~ ls /lib64/modules 4.13.16-35.current 4.14.3-37.current 4.14.5-39.current 4.14.8-41.current 4.14.11-43.current 4.14.4-38.current 4.14.6-40.current 4.14.9-42.current py ~ du -sh /lib64/modules 1006M /lib64/modules