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cd /var/tmp/

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https://www.juniper.net/documentation/en_US/vmx17.4/topics/task/installation/vmx-use-cases-installing.html

Edit the config/vmx.conf 

#Configuration on the host side - management interface, VM images etc.

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    identifier                : vmx1   # Maximum 4 characters
    host-management-interface : eth0
    routing-engine-image      : "/home/vmx/vmxlite/images/junos-vmx-x86-64.qcow2"
    routing-engine-hdd        : "/home/vmx/vmxlite/images/vmxhdd.img"
    forwarding-engine-image   : "/home/vmx/vmxlite/images/vFPC.img"

#External bridge configuration
BRIDGES:
- type : external
name : br0           #br-ext # Max 10 characters

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