How to manually switch Mist to Ropsten?

Question

I am new to Ethereum. I have the v.0.8.7 client. It is fully synchronized with the blockchain (see screenshot below: last block seen a minute ago).

I am basing myself on this post.

If I understood correctly, my Client is currently synchronised with Morden (the article really does not explain things in a noob-understanable manner). So I have to swich to Ropsten.

I entered the commands specified at the bottom of the article, and get the following error.

dyn907-72:~ me$ ls  /Users/me/Library/Ethereum/testnet/
chaindata       keystore        testnet_genesis.json
dapp            nodekey
geth            nodes
dyn907-72:~ me$ geth --datadir /Users/me/Library/Ethereum/testnet init testnet_genesis.json
I1122 14:01:12.203789 ethdb/database.go:83] Alloted 16MB cache and 16 file handles to /Users/me/Library/Ethereum/testnet/chaindata
Fatal: failed to read genesis file: open testnet_genesis.json: no such file or directory
dyn907-72:~ me$

Why does it say "no such file exists" please? I m new to geth, needless to say. Thank you.

Answer 1

You need to use the correct relative path or absolute path for your genesis JSON file.

Relative path would be:

geth --datadir ./Library/Ethereum/testnet init ./Library/Ethereum/testnet/testnet_genesis.json

However, with the absolute you are on the best path:

 geth --datadir /Users/sam/Library/Ethereum/testnet init /Users/sam/Library/Ethereum/testnet/testnet_genesis.json