i tried to make flashdisk directory to ftp server by mount it and change proftpd configuration but still same because the directory is of ftp server is directory system only ? sorry for my bad english

Welcome to LQ!!!

Could you please be more detailed and specific on what you are trying to achieve?

when i try to logging to ftp i tried type ftp.xxx.com but the answer is {530 User ftp cannot log in.} and this is proftpd

Can you share your proftpd configuration file. Also, share the distribution you are using. Do you have anonymous enabled for this ftp server? If yes, did you try logging in with anonymous account. If it not enabled did you try enabling it and test if that works.

i'm using linux debian 7.8

i was already mount my flashdisk

this is my proftpd.conf
________________________________________________________________________________________
#
# /etc/proftpd/proftpd.conf -- This is a basic ProFTPD configuration file.
# To really apply changes, reload proftpd after modification, if
# it runs daemon mode.It is not required in inetd/xinetd mode.
#

# Includes DSO modules
Include /etc/proftpd/modules.conf

# Set off to disable IPV6 support which is annoying on IPV4 only boxes.
UseIPV6 off
# If set you can experience a longer connection delay in many cases.
IdentLookups on

ServerName "xxx.com
ServerType standalone
DeferWelcome on

Multiline2228 on
DefaultServer on
ShowSymlink on

TimeoutNoTransfer 600
TimeoutStalled 600
TimeoutIdle 1200

DisplayLogin welcome.msg
DisplayChdir .massage true
ListOptions "-l"

DenyFilter \*.*/

# Use this to jail all users in their homes
DefaultRoot ~

# Users require a valid shell listed in /etc/shells to login.
# Use this directive to release that constrain.
# RequireValidShell off

# Port 21 is standart FTP port.
Port 21

# In some cases you have to specify passive ports range to by-pass
# firwall limitations.Ephemeral ports can be used for that,but
# fell free to use a more narrow range.
# PassivePorts 49152 65534

# If your host was NATted,this option is useful in order to
# allow passive transfer to work. You have to use your public
# address and opening the passive ports used on your firewall ass well.
MasqueradeAddress 1.2.3.4

# This is useful for masquerading address with dynamic IPs:
# refresh any configured MasqueradeAddress directives every 8 hours
<IfModule mod_dynmasq.c>
# DynMasqRefresh 28800
</IfModule>

# To Prevent DoS attack,set the maximum number of child processes
# to 30. If you need to allow more than 30 concurrent connections
# at once,simply increase this value. Note that this ONLY works
# in standalone mode, in inetd mode you should use an inetd server
# that allows you to limit maximum number of processes per service
# (such as xinetd)
MaxInstances 30

# Set the user and group that the server normally runs at.
User proftpd
Group nogroup

# Umask 022 is a good standart umask to prevent new files and dirs
# (second parm) form being group and world writable.
Umask 022 022
# Normally,we want files to be overwriteable.
AllowOverwrite on

# Uncomment this if you are using NIS or LDAP via to retrive passwords:
# PersistentPasswd off

# This is required to use both PAM-based authentication and local passwords
# AuthOrder mod_auth_pam.c* mod_auth_unix.c

# Be warned: use of this directive impacts CPU averange load!
# Uncomment this if you like to see progress and transfer rate with ftpwho
# in downloads. That is not needed for uploads rates.
#
# UseSendFile off

TransferLog /var/log/proftpd/xferlog
SystemLog /var/log/proftpd/proftpd.log

# logging onto /var/log/lastlog is enabled but set to off by default
#UseLastlog on

# In order to keep log file dates consistent after chroot, use timezone info
# from /etc/localtime. If this is not set, and proftpd is configured to
# chroot (e.g. DefaultRoot or <Anonymous>), it will use the non-daylight
# saving timezone regardless of whether DST is in affect.
#SetEnv TZ :/etc/localtime

<IfModule mod_quotatab.c>
QuotaEngine off
</IfModule>

<IfModule mod_ratio.c>
Ratio off
</IfModule>


# Delay engine reduces impact of the so-called Timing Attack described in
# http://www.securityfocus.com/bid/11430/discuss
# It is on by default.
<IfModule mod_delay.c>
DelayEngine on
</IfModule>

<IfModule mod_ctrls.c>
ControlsEngine off
ControlsMaxClients 2
ControlsLog /var/log/proftpd/control.log
ControlsInterval 5
ControlsSocket /var/run/proftpd/proftpd.sock
</IfModule>

<IfModule mod_ctrl_admin.c
AdminsControlsEngine off
</IfModule>

#
# Alternative authentication frameworks
#
#Include /etc/proftpd/ldap.conf
#Include /etc/proftpd/sql.conf

#
# This is used for FTPS connections
#
#Include /etc/proftpd/tls.conf

#
# Useful to keep VirtualHost/VirtualRoot directives seperated
#
#Include /etc/proftpd/virtuals.conf

# A basic anonymous configuration, no upload directories.

<Anonymous /media/FD>
User ftp
Group nogroup
# We want client to be able to login with "anonymous" as well as "ftp"
UserAlias anonymous ftp
# Cosmetic changes,all files belong to ftp user
DirFakeUser on ftp
DirFakeGroup on ftp

RequireValidShell off

# Limit the maximum number of anonymous logins
MaxClient 10

# We want 'welcome.msg' displayed at login,and '.massage' displayed
# in each newly chdired directory.
DisplayLogin welcome.msg
DisplayChdir .massage

# Limit WRITE everywhere in the anonymous chroot
<Directory *>
<Limit WRITE>
DenyAll
</Limit>
</Directory>

# Uncomment this if you're brave.
# <Directory incoming>
# # Umask 022 is a good standart umask to prevent new file and dirs
# # (second parm) from being group and world writable.
# Umask 022 022
# <Limit READ WRITE>
# DenyAll
# </Limit>
# <Limit STOR>
# AllowAll
# </Limit>
# </Directory>

</Anonymous /media/FD>
________________________________________________________________________________________

Few things to check:

1. Does user FTP has got access to: /media/FD directory.
2. Does user FTP has got valid shell, you can check that by running:

If it says /sbin/nologin change it to /bin/bash

This is a customized location which you want your anonymous FTP user to access. Did you try it with default one? Did it work?