Hello, so you can't really change the boot device. What is it you are really trying to accomplish?
What you are looking at there are PRPs in 4 and 5 and different linecards in the others, correct? The RPs will boot off disk0. While the linecards will memboot after the PRPs have come up. This is normal.
You can have a PRP do a memboot, but this is not supported for production routers. The down side would be you can't later add packages or SMUs. This is usually only done in a lab environment.
As for different boot devices, you can have disk0: disk1: as devices on the PRPs.
Take a look at the following doc for setting up disk mirroring and backups and such.
Introduction: The "external-out enable" command is available for
configuration under the "router ospf process" in case of the IOS-XR
operating system. This command basically enables advertisement of
intra-area routes on the device as external routes in th...
Introduction Basic configuration for netflow Scale parameters for
netflow Netflow support Architecture Packet flow for netflow Inside the
LC CPU Netflow Cache size, maintenance and memory Sample usage Cache
Size Aging Permanent cache Characteristics Which...