I'm using OpenSSH from a Windows machine to connect to a Linux Mint 9 box. My Windows user name doesn't match the ssh target's user name, so I'm trying to specify the user to use for login using ssh_config. I know OpenSSH can see the ssh_config file since I'm specifying the identify file in it.

The section specific to the host in ssh_config is:

  Host hostname
    HostName      hostname
    IdentityFile  ~/.ssh/id_dsa
    User          username
    Compression   yes

If I do ssh username@hostname it works.

Trying using ssh_config only gives:

F:\>ssh -v hostname
OpenSSH_5.6p1, OpenSSL 0.9.8o 01 Jun 2010
debug1: Connecting to hostname [XX.XX.XX.XX] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /cygdrive/f/progs/OpenSSH/home/.ssh/id_rsa type -1
debug1: identity file /cygdrive/f/progs/OpenSSH/home/.ssh/id_rsa-cert type -1
debug1: identity file /cygdrive/f/progs/OpenSSH/home/.ssh/id_dsa type 2
debug1: identity file /cygdrive/f/progs/OpenSSH/home/.ssh/id_dsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3p1 Debia
n-3ubuntu5
debug1: match: OpenSSH_5.3p1 Debian-3ubuntu5 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.6
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host 'hostname' is known and matches the RSA host key.
debug1: Found key in /cygdrive/f/progs/OpenSSH/home/.ssh/known_hosts:1
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /cygdrive/f/progs/OpenSSH/home/.ssh/id_rsa
debug1: Offering DSA public key: /cygdrive/f/progs/OpenSSH/home/.ssh/id_dsa
debug1: Authentications that can continue: publickey
debug1: No more authentication methods to try.
Permission denied (publickey).

I was under the impression that (as outlined in this question: How to make ssh log in as the right user?) specifying User username in ssh_config should work.

Why isn't OpenSSH using the username specified in ssh_config?