I have written C software that makes extensive use of shared memory (200MB using shmget, etc.), which compiled and ran on Mojave and Linux. Using this shared memory required /etc/sysctl.conf to increase the buffer sizes during OSX boot. It appears that Catalina no longer uses my /etc/sysctl.conf file, whether SIP is enabled or disabled. Now the software compiles but fails to run, because the default shared memory size (4MB) is too small on Catalina. How do I specify the shared memory parameters to increase above the default in Catalina? kern.sysv.shmmax=268435456 kern.sysv.shmmin=1 #kern.sysv.shmmni=128 kern.sysv.shmseg=32 kern.sysv.shmall=65536