APT_PM_STARTUP_CONCURRENCY
Set the APT_PM_STARTUP_CONCURRENCY environment variable to a small integer to determine the number of simultaneous section leader startups to be allowed.
Set APT_PM_STARTUP_CONCURRENCY to 1 forces sequential startup. The default is defined by SOMAXCONN in sys/socket.h (currently 5 for Solaris, 10 for AIX®).