csr1000v images -*serial.qcow2 vs *.qcow2 can someone explain the differences

[dogoldsh]

i want do understand what the difference between the images and when i need to use the file name that include the -serial.qcow2 on the image name

for example:

csr1000v-universalk9.16.08.01a.qcow2

vs

csr1000v-universalk9.16.08.01a-serial.qcow2

i see same images on other previews version

i didn't find any document that explain the difference and when to use the *-serial.qcow2

[rbergeon]

Found it - check 

https://www.cisco.com/c/en/us/td/docs/routers/csr1000/software/configuration/b_CSR1000v_Configuration_Guide/b_CSR1000v_Configuration_Guide_chapter_0101.html - section creating KVM images for OpenStack 

You need the serial image if you want a serial connection for the OpenStack dashboard