Assuming you have no router/swicthes available (Juniper) and you need to create from scratch a basic config (it is not important the specific content of the config here) which later will be load in the router (e.g. mx-960)via usb.
How can I create this file from scratch without using any Router/Swicthes?
I read that the file has to be ASCII file but I am not sure how to create it and make it readible from the device.
Can you please provide more info on the requirement? If you need to create the initial configuration, please refer the following
The config can be loaded using
load set <filename>
load merge <filename>
depending on whether it is in set format or not.
Please refer the following to mount the USB with the config file
The configuration file which you want to make offline can be a plain text file [made with notepad in windows or VI editor in unix] and later you can use to upload it to the box. Copy the file to the local router, and then load the file into the CLI. After you have loaded the file, you can commit it to activate the configuration on the router, or you can edit the configuration interactively using the CLI and commit it at a later time.
You can also create a configuration while typing at the terminal and then load it. Loading a configuration from the terminal is generally useful when you are cutting existing portions of the configuration and pasting them elsewhere in the configuration.
To load an existing configuration file that is located on the router, use the load configuration mode command:
user@host# load (factory-default | merge | override | patch | replace | set | update) filename <relative> <json>
To load a configuration from the terminal, use the following version of the load configuration mode command. Press Ctrl-d to end the input.
user@host# load (factory-default | merge | override | patch | replace | set | update)
terminal <relative> <json>