I found network-related config from one test leaking into another and making the latter test fail, despite my use of what I thought was everything required to keep them separate (unix_sock_dir and log_outputs both set in config, and --pid-file specified on command line). Unfortunately, there are still hard-coded references to some files. /* Configuration paths are either ~/.libvirt/qemu/... (session) or * /etc/libvirt/qemu/... (system). That's from network_driver.c, to set these variables: struct network_driver ->networkConfigDir ->networkAutostartDir However, storage_driver is nearly identical in that respect. It also uses ~/.libvirt/ vs SYSCONF_DIR/libvirt. Same for uml_driver.c. So, rather than adding new variables for each of these six new parameters, how about just one new config parameter to allow specification of a directory prefix that would replace "~" and "/etc" in determining how to form config-related names? Being able to run multiple libvirtd processes in parallel without having one affect another is a hard requirement for any serious testing.