proftpd 权限限制
CMD：Change Working Directory 改变目录
CDUP/XCUP： change to parent directory 即CD ..
CWD/XCWD ：change working directory 即CD
MKD/XMKD：MaKe Directory 建立目录的权限
RNFR/RNTO： rename from/rename to一般在一起用
DELE：DELEte 删除文件的权限
RMD/XRMD：ReMove Directory 删除空目录的权限
RETR：RETRieve 从服务端下载到客户端的权限
STOR： store 上传存在则覆盖
STOU： store unique 上传并随机生成文件名存储
APPE： append 续上传不存在则新建
ALLO： allocate 请求服务器磁盘空间
REST： restart 重新开始（必须后跟RETR，STOR，APPE）
READ：可读的权限，不包括列目录的权限，相当于RETR，STAT等
WRITE：写文件或者目录的权限，包括MKD和RMD
DIRS：是否允许列目录，相当于LIST，NLST等权限，还是比较实用的
ALL：所有权限
LOGIN：是否允许登陆的权限
针对上面这个Limit所应用的对象，又包括以下范围
AllowUser 针对某个用户允许的Limit
DenyUser 针对某个用户禁止的Limit
AllowGroup 针对某个用户组允许的Limit
DenyGroup 针对某个用户组禁止的Limit
AllowAll 针对所有用户组允许的Limit
DenyAll 针对所有用户禁止的Limit
Order allow,deny参见apache的文章
http://www.fwolf.com/blog/post/191
http://blog.csdn.net/yjz0065/archive/2007/11/08/1873763.aspx
关于限制速率的参数为：
TransferRate STOR|RETR 速度（Kbytes/s） user 使用者
MaxClientsPerHost 数目
MORE:http://www.castaglia.org/proftpd/doc/contrib/ProFTPD-mini-HOWTO-ConfigurationTricks.html
http://www.proftpd.org/docs/contrib/mod_ifsession.html
http://www.proftpd.org/docs/contrib/
Name
Limit -- Set the commands/actions to be controlled
Synopsis
Limit [ <Limit command|command-group [command2 ..]>;]
Default
None
Context
server config, <VirtualHost>;, <Directory>;, <Anonymous>;, <Global>;, .ftpaccess
Module
mod_core
Compatibility
0.99.0 and later
Description
The Limit configuration block is used to place access restrictions on one or more FTP commands, within a given context. Limits flow downward, so that a Limit configuration in the server config context applies to all <Directory>; and <Anonymous>; blocks that also reside in the configuration; until it is overridden by a "lower" <Limit>; block. Any number of command parameters can be specified, against which the contents of the <Limit>; block will be applied. command can be any valid FTP command, but is generally one of the following: CWD (Change Working Directory) Sent by client when changing directories. MKD / XMKD (MaKe Directory) Sent by client to create a new directory. RNFR (ReName FRom), RNTO (ReName TO) Sent as a pair by client to rename a directory entry. DELE (DELEte) Sent by client to delete a file. RMD / XRMD (ReMove Directory) Sent by client to remove a directory. RETR (RETRieve) Transfer a file from the server to the client. STOR (STORe) Transfer a file from the client to the server. In addition, the following command-groups are accepted. They have a lower precedence than real commands, meaning that a real command limit will always be applied instead of the command-group. READ All FTP commands which deal with file reading (directory listing not included): RETR, SITE, SIZE, STAT WRITE All FTP commands which deal with file or directory write/creation/deletion: APPE, DELE, MKD, RMD, RNTO, STOR, XMKD, XRMD DIRS All FTP commands which deal with directory listing: CDUP, CWD, LIST, MDTM, NLST, PWD, RNFR, XCUP, XCWD, XPWD ALL ALL FTP commands (identical to READ WRITE DIRS). Note this group has the lowest precedence of all; it will not override a limit imposed by another command-group (e.g. DIRS). Finally, a special command is allowed which can be used to control login access: LOGIN Connection or login to the server. Applying a <Limit>; to this pseudo-command can be used to allow or deny initial connection or login to the context. It has no effect, and is ignored, when used in a context other than server config, <VirtualHost>; or <Anonymous>; (i.e. using it in a <Directory>; context is meaningless). <Limit>; command restrictions should not be confused with file/directory access permission. While limits can be used to restrict a command on a certain directory, they cannot be used to override the file permissions inherent to the base operating/file system. The following FTP commands cannot be restricted via <Limit>;: ABOR HELP MODE (not implemented, always S) NOOP PASS (use <Limit LOGIN>) PASV PORT QUIT REST (use AllowRetrieveRestart, AllowStoreRestart) STRU (not implemented, always F) SYST TYPE USER (use <Limit LOGIN>)
