How to do paper backup and restore for bitcoin core Since bitcoin core is HD wallet, it should be possible to make "seed" like backup for it and there should be way to restore the wallet from it as well. I know there is dumpprivkey, but it needs to be done after every transaction to be safe. Other wallets have nice seed backup and restore methods, I suppose core should have one as well. 

There is xprv method mentioned in comments, but I'm still missing restore method. Also I would like to do it from console only, since my wallet is on remote server without graphics. 

I'm interested in "string" backup mainly because I want to store it in trezor hardware password manager, which does not support files
Bitcoin Core does not allow you to restore from a given seed or master private key (xprv). There is currently no mechanism for importing seeds or master private keys and no mechanism for exporting seeds (and a convoluted workaround for exporting master private keys).

Note that you can import individual private keys, not just seeds, mnemonics, or master private keys. These can be imported with importmulti or importprivkey and can be exported with dumpprivkey.