我对 OTP ssh 守护进程实现的行为有点困惑，我想知道是否有人可以为我解决问题。预赛；我有以下程序：
-module(sshd).
-export([start/0, stop/1]).
-spec start() -> {ok, ssh:ssh_daemon_ref()} | {error, atom()}.
start() ->
_ = application:start(crypto),
_ = application:start(ssh),
Opts = [
{system_dir, "/etc/erl_sshd/"},
{pwdfun, fun passwd/2}
],
ssh:daemon(2222, Opts).
-spec stop(ssh:ssh_daemon_ref()) -> ok.
stop(Ref) ->
ssh:stop_daemon(Ref).
%% ===================================================================
%% Internal Functions
%% ===================================================================
-spec passwd(User::string(), Password::string()) -> boolean().
passwd(User, User) ->
true;
passwd(_User, _Password) ->
false.
并/tmp/erl_sshd在磁盘上创建如下：
> mkdir /tmp/erl_sshd
> ssh-keygen -t rsa -f /tmp/erl_sshd/ssh_host_rsa_key
Generating public/private rsa key pair.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /tmp/erl_sshd/ssh_host_rsa_key.
Your public key has been saved in /tmp/erl_sshd/ssh_host_rsa_key.pub.
The key fingerprint is:
...
使用 OpenSSHd 进行测试：
> /usr/sbin/sshd -p 2222 -h /tmp/erl_sshd/ssh_host_rsa_key -d
debug1: sshd version OpenSSH_5.6p1
debug1: read PEM private key done: type RSA
debug1: private host key: #0 type 1 RSA
debug1: setgroups() failed: Operation not permitted
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-p'
debug1: rexec_argv[2]='2222'
debug1: rexec_argv[3]='-h'
debug1: rexec_argv[4]='/tmp/erl_sshd/ssh_host_rsa_key'
debug1: rexec_argv[5]='-d'
debug1: Bind to port 2222 on 0.0.0.0.
Server listening on 0.0.0.0 port 2222.
debug1: Bind to port 2222 on ::.
Server listening on :: port 2222.
我可以得到提示没问题：
> ssh localhost -p 2222 -v
OpenSSH_5.6p1, OpenSSL 0.9.8r 8 Feb 2011
debug1: Reading configuration data /etc/ssh_config
debug1: Applying options for *
debug1: Applying options for *
debug1: Connecting to localhost [::1] port 2222.
debug1: Connection established.
debug1: identity file /Users/blt/.ssh/id_rsa type 1
debug1: identity file /Users/blt/.ssh/id_rsa-cert type -1
debug1: identity file /Users/blt/.ssh/id_dsa type -1
debug1: identity file /Users/blt/.ssh/id_dsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.6
debug1: match: OpenSSH_5.6 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: checking without port identifier
The authenticity of host '[localhost]:2222 ([::1]:2222)' can't be established.
RSA key fingerprint is 01:0e:c6:0b:f4:48:ab:0a:49:2a:66:38:27:67:8f:52.
Are you sure you want to continue connecting (yes/no)? ^C
但是，当我启动 erlang sshd 时：
> erl
Erlang R15B03 (erts-5.9.3) [source] [64-bit] [smp:8:8] [async-threads:0] [hipe] [kernel-poll:false]
Eshell V5.9.3 (abort with ^G)
1> c(sshd), {ok, Ref} = sshd:start().
{ok,<0.49.0>}
2>
没运气：
> ssh localhost -p 2222 -v
OpenSSH_5.6p1, OpenSSL 0.9.8r 8 Feb 2011
debug1: Reading configuration data /etc/ssh_config
debug1: Applying options for *
debug1: Applying options for *
debug1: Connecting to localhost [::1] port 2222.
debug1: Connection established.
debug1: identity file /Users/blt/.ssh/id_rsa type 1
debug1: identity file /Users/blt/.ssh/id_rsa-cert type -1
debug1: identity file /Users/blt/.ssh/id_dsa type -1
debug1: identity file /Users/blt/.ssh/id_dsa-cert type -1
debug1: Remote protocol version 2.0, remote software version Erlang
debug1: no match: Erlang
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-cbc hmac-sha1 none
debug1: kex: client->server aes128-cbc hmac-sha1 none
no hostkey alg
除了创建用户之外，我还完成了用户指南中概述的相同步骤，并涵盖了与此问题相同的基础。我在 OS X 系统上：
> sw_vers
ProductName: Mac OS X
ProductVersion: 10.7.5
BuildVersion: 11G63
如果我以 root 用户身份运行 erlang shell 并按预期重定向system_dir到所有工作。/etc其他人清楚这是怎么回事吗？/tmp/erl_sshd也许erlang 正在悄悄出错的目录的用户权限？我之前打开了 sasl 应用程序，但输出中没有任何相关的内容对我产生影响。