$ sudo virsh list --all
 Id    Name                           State
 1     centos7                        running
 -     centos8                        shut off

$ sudo virsh autostart centos7


$ sudo nano /etc/default/libvirt-guests 
# URIs to check for running guests
# example: URIS='default xen:/// vbox+tcp://host/system lxc:///'

# action taken on host boot
# - start   all guests which were running on shutdown are started on boot
#           regardless on their autostart settings
# - ignore  libvirt-guests init script won't start any guest on boot, however,
#           guests marked as autostart will still be automatically started by
#           libvirtd

# Number of seconds to wait between each guest start. Set to 0 to allow
# parallel startup.

# action taken on host shutdown
# - suspend   all running guests are suspended using virsh managedsave
# - shutdown  all running guests are asked to shutdown. Please be careful with
#             this settings since there is no way to distinguish between a
#             guest which is stuck or ignores shutdown requests and a guest
#             which just needs a long time to shutdown. When setting
#             ON_SHUTDOWN=shutdown, you must also set SHUTDOWN_TIMEOUT to a
#             value suitable for your guests.

# Number of guests will be shutdown concurrently, taking effect when
# "ON_SHUTDOWN" is set to "shutdown". If Set to 0, guests will be shutdown one
# after another. Number of guests on shutdown at any time will not exceed number
# set in this variable.

# Number of seconds we're willing to wait for a guest to shut down. If parallel
# shutdown is enabled, this timeout applies as a timeout for shutting down all
# guests on a single URI defined in the variable URIS. If this is 0, then there
# is no time out (use with caution, as guests might not respond to a shutdown
# request). The default value is 300 seconds (5 minutes).

# If non-zero, try to bypass the file system cache when saving and
# restoring guests, even though this may give slower operation for
# some file systems.

# If non-zero, try to sync guest time on domain resume. Be aware, that
# this requires guest agent with support for time synchronization
# running in the guest. For instance, qemu-ga doesn't support guest time
# synchronization on Windows guests, but Linux ones. By default, this
# functionality is turned off.


$ sudo nano /etc/sysconfig/libvirt-guests