I have installed zcash wallet on cli linux, but i cannot find the command how to unlock my wallet. Is there any?
right now wallet encryption is still being added back in....when zcash forked from bitcoin 0.11.2 they disabled it, because you have to have the private key(s) for the private addresses, aka "z-addrs" that are in your wallet available when the blockchain is scanned on startup to be able to tell which, if any, transactions involve your addresses.
So if the wallet is locked, you couldn't scan the blockchain (or you'd have to do it again with a zcashd restart when you unlocked it). Adding wallet encryption back in is therefore much more complicated in zcash, but code for it is in the works.
So you shouldn't need to unlock it....somebody else jump in and correct me if any of those details are wrong!