Could not resize shared memory segment error I have a PostgreSQL 11.2 (Debian 11.2-1.pgdg90+1) running in a docker container.
I get the following error with some queries:

could not resize shared memory segment &quot;/PostgreSQL.860708388&quot; to 536870912 bytes: No space left on device`

system:

Ubuntu 18.04.5
memory: 126 GB
cores: 64

disk usage is fine, as well as quotas.
Postgres settings:

work_mem: 30GB,
dynamic_shared_memory_type: posix
max_parallel_workers_per_gather: 32
Lowering number on max_parallel_workers_per_gather to 8 seems to have fixed the problem in my case.