建立虚拟用户
[root@rhel4 opt]# cat << ! >logins.txt 说明：此文本文件的格式是：单数行为用户名，偶数行为密码
> upload
> 123456
> download
> 123456
> admin
> 123456
> !

[root@rhel4 opt]# db_load -T -t hash -f logins.txt /etc/vsftpd_login.db
[root@rhel4 opt]# chmod 600 /etc/vsftpd_login.db
[root@rhel4 opt]# cd /opt/vsftpd-1.2.1/EXAMPLE/VIRTUAL_USERS (进入解包的源码目录，把虚拟用户的认证文件拷贝到/etc/pam.d/下)
[root@rhel4 VIRTUAL_USERS]# cp vsftpd.pam /etc/pam.d/ftp.vu
(建立虚拟用户所要访问的ftp目录并设置仅virtual用户访问的权限和创建一个供下载实验的文件)
[root@rhel4 VIRTUAL_USERS]# mkdir /var/ftpsite
[root@rhel4 VIRTUAL_USERS]# useradd -d /var/ftpsite virtual;
[root@rhel4 VIRTUAL_USERS]# chmod 700 /var/ftpsite
[root@rhel4 VIRTUAL_USERS]# chown virtual /var/ftpsite
[root@rhel4 VIRTUAL_USERS]# su - virtual -c "echo hello >/var/ftpsite/test.file"
vi /etc/vsftpd.conf在此文件中插入下面的配置语句
guest_enable=YES（启用虚拟用户）
guest_username=virtual（将虚拟用户映射为本地virtual用户）
pam_service_name=ftp.vu（指定PAM配置文件为ftp.vu）
user_config_dir=/etc/vsftpd_user_conf（指定不同虚拟用户配置文件的存放路径）
[root@rhel4 VIRTUAL_USERS]# mkdir /etc/vsftpd_user_conf
h.开放不同用户的不同权限　echo "anon_world_readable_only=NO"> /etc/vsftpd_user_conf/download（开放download用户的下载权限——只能下载；注意这个不地方不要写成YES，否则将不能列出文件和目录）
cp /etc/vsftpd_user_conf/download /etc/vsftpd_user_conf/upload
vi /etc/vsftpd_user_conf/upload，添加下列行
write_enable=YES （增加写权限）
anon_upload_enable=YES（增加上传权限）
anon_mkdir_write_enable=YES (增加创建目录的权限）
cp /etc/vsftpd_user_conf/upload /etc/vsftpd_user_conf/admin
增加一行：
anon_other_write_enable=YES（增加管理员用户的删除/重命名的权限）
i.测试
killall -9 vsftpd;/usr/local/sbin/vsftpd /etc/vsftpd.conf &
ftp 127.0.0.1 2121
以用户名download和你设置的密码登录，ls，可以看到文件，下载，成功！put一个文件，提示
Permission denied。rename test.file同样权限被拒绝；delete test.file同样不成功！
输入quit退出，以upload用户登录，OK！可以上传，下载，mkdir lsf，提示“/lsf" created；rename lsf lsf1提示Permission denied,删除文件同样不成功！
输入quit退出，以admin用户登录，可以有上述所有权限，然后rmdir lsf,提示Remove directory o [eration successful;delete test.file提示Delete operation successful!OK，大功告成了！

参考：
http://www.linuxts.com/modules/sections/index.php?op=printpage&artid=2206&PHPSESSID=e1a0ec323f0f75bc59cbb83afeeb59ff
http://www.uplinux.com/www/net/02/117.shtml
附
1.我的/etc/vsftpd.conf文件的内容
[root@rhel4 VIRTUAL_USERS]# cat /etc/vsftpd.conf
# Example config file /etc/vsftpd.conf
#
# The default compiled in settings are fairly paranoid. This sample file
# loosens things up a bit, to make the ftp daemon more usable.
# Please see vsftpd.conf.5 for all compiled in defaults.
#
# READ THIS: This example file is NOT an exhaustive list of vsftpd options.
# Please read the vsftpd.conf.5 manual page to get a full idea of vsftpd's
# capabilities.
#
# Allow anonymous FTP? (Beware - allowed by default if you comment this out).
anonymous_enable=YES
#
# Uncomment this to allow local users to log in.
local_enable=YES
#
# Uncomment this to enable any form of FTP write command.
write_enable=YES
#
# Default umask for local users is 077. You may wish to change this to 022,
# if your users expect that (022 is used by most other ftpd's)
local_umask=022
#
# Uncomment this to allow the anonymous FTP user to upload files. This only
# has an effect if the above global write enable is activated. Also, you will
# obviously need to create a directory writable by the FTP user.
#anon_upload_enable=YES
#
# Uncomment this if you want the anonymous FTP user to be able to create
# new directories.
#anon_mkdir_write_enable=YES
#
# Activate directory messages - messages given to remote users when they
# go into a certain directory.
dirmessage_enable=YES
#
# Activate logging of uploads/downloads.
xferlog_enable=YES
#
# Make sure PORT transfer connections originate from port 20 (ftp-data).
connect_from_port_20=YES
#
# If you want, you can arrange for uploaded anonymous files to be owned by
# a different user. Note! Using "root" for uploaded files is not
# recommended!
#chown_uploads=YES
#chown_username=whoever
#
# You may override where the log file goes if you like. The default is shown
# below.
#xferlog_file=/var/log/vsftpd.log
#
# If you want, you can have your log file in standard ftpd xferlog format
#xferlog_std_format=YES
#
# You may change the default value for timing out an idle session.
#idle_session_timeout=600
#
# You may change the default value for timing out a data connection.
#data_connection_timeout=120
#
# It is recommended that you define on your system a unique user which the
# ftp server can use as a totally isolated and unprivileged user.
#nopriv_user=ftpsecure
#
# Enable this and the server will recognise asynchronous ABOR requests. Not
# recommended for security (the code is non-trivial). Not enabling it,
# however, may confuse older FTP clients.
#async_abor_enable=YES
#
# By default the server will pretend to allow ASCII mode but in fact ignore
# the request. Turn on the below options to have the server actually do ASCII
# mangling on files when in ASCII mode.
# Beware that turning on ascii_download_enable enables malicious remote parties
# to consume your I/O resources, by issuing the command "SIZE /big/file" in
# ASCII mode.
# These ASCII options are split into upload and download because you may wish
# to enable ASCII uploads (to prevent uploaded scripts etc. from breaking),
# without the DoS risk of SIZE and ASCII downloads. ASCII mangling should be
# on the client anyway..
#ascii_upload_enable=YES
#ascii_download_enable=YES
#
# You may fully customise the login banner string:
#ftpd_banner=Welcome to blah FTP service.
#
# You may specify a file of disallowed anonymous e-mail addresses. Apparently
# useful for combatting certain DoS attacks.
#deny_email_enable=YES
# (default follows)
#banned_email_file=/etc/vsftpd.banned_emails
#
# You may specify an explicit list of local users to chroot() to their home
# directory. If chroot_local_user is YES, then this list becomes a list of
# users to NOT chroot().
#chroot_list_enable=YES
# (default follows)
#chroot_list_file=/etc/vsftpd.chroot_list
#
# You may activate the "-R" option to the builtin ls. This is disabled by
# default to avoid remote users being able to cause excessive I/O on large
# sites. However, some broken FTP clients such as "ncftp" and "mirror" assume
# the presence of the "-R" option, so there is a strong case for enabling it.
#ls_recurse_enable=YES
guest_enable=YES
guest_username=virtual
pam_service_name=ftp.vu
user_config_dir=/etc/vsftpd_user_conf
max_clients=500
max_per_ip=50
local_max_rate=100000
anon_max_rate=10000
pasv_enable=yes
pasv_min_port=50000
pasv_max_port=60000
idle_session_timeout=600
data_connection_timeout=120
accept_timeout=60
connect_timeout=60
listen=YES

2.我的/etc/vsftpd_user_conf/download的内容
[root@rhel4 VIRTUAL_USERS]# cat /etc/vsftpd_user_conf/download
anon_world_readable_only=NO
3.我的/etc/vsftpd_user_conf/upload的内容
[root@rhel4 VIRTUAL_USERS]# cat /etc/vsftpd_user_conf/upload
anon_world_readable_only=NO
write_enable=YES
anon_upload_enable=YES
anon_mkdir_write_enable=YES
4.我的/etc/vsftpd_user_conf/admin的内容
[root@rhel4 VIRTUAL_USERS]# cat /etc/vsftpd_user_conf/admin
anon_world_readable_only=NO
write_enable=YES
anon_upload_enable=YES
anon_mkdir_write_enable=YES
anon_other_write_enable=YES