为何无法登录嵌入式linux？

ykai007

内核：2.6.20
在嵌入式Linux里面有root用户和transmit用户,并可以通过su切换用户,但是有如下错误:
/bin/sh: can't access tty; job control turned off
网上说可以通过修改inittab,但是我试过了无效.
嵌入式Linux里含有/etc/passwd,/etc/shadow,/etc/group文件,是否建立一个完整的linux帐号还需要其他什么文件?
以下的pure-ftpd在PC机上同样配置情况下可以正常登录,所以应该不是ftpd的配置问题.
使用inetutils ftpd:
[root@localhost etc]# ftp 192.168.2.24
220 192.168.2.24 FTP server ready.
500 'AUTH GSSAPI': command not understood.
500 'AUTH KERBEROS_V4': command not understood.
KERBEROS_V4 rejected as an authentication type
Name (192.168.2.24:root): root
530 User root access denied.
Login failed.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> user
(username) transmit
530 User transmit access denied.
Login failed.

使用bftpd:
[root@localhost etc]# ftp 192.168.2.24
Connected to 192.168.2.24.
220 bftpd 2.0 at 192.168.2.24 ready.
500 Unknown command: "AUTH GSSAPI"
500 Unknown command: "AUTH KERBEROS_V4"
KERBEROS_V4 rejected as an authentication type
Name (192.168.2.24:root): root
331 Password please.
Password:
421 Login incorrect.
Login failed.
No control connection for command: No such file or directory
ftp> user
Not connected.
ftp> open 192.168.2.24
Connected to 192.168.2.24.
220 bftpd 2.0 at 192.168.2.24 ready.
500 Unknown command: "AUTH GSSAPI"
500 Unknown command: "AUTH KERBEROS_V4"
KERBEROS_V4 rejected as an authentication type
Name (192.168.2.24:root): transmit
331 Password please.
Password:
421 Login incorrect.
Login failed.
No control connection for command: No such file or directory

使用pure-ftpd:
[root@localhost /]# ftp 192.168.2.24
Connected to 192.168.2.24.
220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
220-You are user number 1 of 50 allowed.
220-Local time is now 00:09. Server port: 21.
220-This is a private system - No anonymous login
220 You will be disconnected after 15 minutes of inactivity.
500 This security scheme is not implemented
500 This security scheme is not implemented
KERBEROS_V4 rejected as an authentication type
Name (192.168.2.24:root): root
331 User root OK. Password required
Password:
530 Login authentication failed
Login failed.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> user
(username) transmit
331 User transmit OK. Password required
Password:
530 Login authentication failed
Login failed.
ftp> bye
221-Goodbye. You uploaded 0 and downloaded 0 kbytes.
221 Logout.

仅开发匿名模式的pure-ftpd:
ftp> open 192.168.2.24
Connected to 192.168.2.24.
220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
220-You are user number 1 of 50 allowed.
220-Local time is now 00:02. Server port: 21.
220-Only anonymous FTP is allowed here
220 You will be disconnected after 15 minutes of inactivity.
500 This security scheme is not implemented
500 This security scheme is not implemented
KERBEROS_V4 rejected as an authentication type
Name (192.168.2.24:root): anonymous
421 Service not available, remote server has closed connection
Login failed.
No control connection for command: No such file or directory
ftp>