Linux下实现FTP服务的软件很多,最常见的有vsftpd,Wu-ftpd和Proftp等.Red Hat Enterprise Linux中默认安装的是vsftpd。
访问FTP服务器时需要经过验证,只有经过了FTP服务器的相关验证,用户才能访问和传输文件.vsftpd提供了3种ftp登录形式:
(1)anonymous(匿名帐号)
使用anonymous是应用广泛的一种FTP服务器.如果用户在FTP服务器上没有帐号,那么用户可以以anonymous为用户名,以自己的电子邮件地址为密码进行登录.当匿名用户登录FTP服务器后,其登录目录为匿名FTP服务器的根目录/var/ftp.为了减轻FTP服务器的负载,一般情况下,应关闭匿名帐号的上传功能.
(2)real(真实帐号)
real也称为本地帐号,就是以真实的用户名和密码进行登录,但前提条件是用户在FTP服务器上拥有自己的帐号.用真实帐号登录后,其登录的目录为用户自己的目录,该目录在系统建立帐号时系统就自动创建.
(3)guest(虚拟帐号)
如果用户在FTP服务器上拥有帐号,但此帐号只能用于文件传输服务,那么该帐号就是guest,guest是真实帐号的一种形式,它们的不同之处在于,geust登录FTP服务器后,不能访问除宿主目录以外的内容.
二.FTP相关配置文件说明
其相关配置文件有/etc/vsftpd/vsftpd.conf, /etc/vsftpd.ftpusers, /etc/vsftpd.user_list,在配置FTP服务器时,主要是修改这些文件中的相关语句.
1.vsftpd.conf文件说明
# Example config file /etc/vsftpd/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 //是否允许anonymous登录FTP服务器,默认是允许的.
#
# Uncomment this to allow local users to log in.
local_enable=YES //是否允许本地用户登录FTP服务器,默认是允许
#
# Uncomment this to enable any form of FTP write command.
write_enable=YES //是否允许用户具有在FTP服务器文件中执行写的权限,默认是允许
#
# 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 //设置本地用户的文件生成掩码为022,默认是077
#
# 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 //是否允许匿名账户在FTP服务器中创建目录
#
# Activate directory messages - messages given to remote users when they
# go into a certain directory.
dirmessage_enable=YES //激活目录信息,当远程用户更改目录时,将出现提示信息
#
# Activate logging of uploads/downloads.
xferlog_enable=YES //启用上传和下载日志功能
#
# Make sure PORT transfer connections originate from port 20 (ftp-data).
connect_from_port_20=YES //启用FTP数据端口的连接请求
#
# 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 //设置日志文件的文件名和存储路径,这是默认的
#
# If you want, you can have your log file in standard ftpd xferlog format
xferlog_std_format=YES//是否使用标准的ftpd xferlog日志文件格式
#
# You may change the default value for timing out an idle session.
#idle_session_timeout=600 //设置空闲的用户会话中断时间,默认是10分钟
#
# You may change the default value for timing out a data connection.
#data_connection_timeout=120//设置数据连接超时时间,默认是120秒.
#
# 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 //是否允许使用ASCII格式来上传和下载文件
#
# You may fully customise the login banner string:
#ftpd_banner=Welcome to blah FTP service.//在FTP服务器中设置欢迎登录的信息.
#
# 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().