Serv-U: quickly build powerful FTP servers

The rapid development of the Internet provides people with unprecedented information resources. More and more people want to enjoy the Internet
With a brand new experience, you can have your own online home. In today's popular Internet applications
File transmission is the most popular. This article will combine the powerful Serv-U, user-friendly, easy to learn and use ftp
Server Software: describes in detail how to build a complete FTP server in the shortest time. In addition to the specific installation and configuration instructions
All the necessary knowledge, hoping to help the majority of users.
Introduction
Serv-U is currently a large number of FTP
Server software. By using Serv-U, users can set any PC as an FTP server, so that users or other users can use ftp
Protocol, by connecting any PC on the same network to the FTP server, copying, moving, creating, and deleting files or directories. FTP
The protocol is used to specify the standards and rules for file transfer between computers.
This special protocol enables people to transmit different types of files through different types of computers using different types of operating systems.
Although the FTP server has a wide variety of software and each has its own advantages, Serv-U is able to show its unique features. Specifically, Serv-U provides the following functions:
User-friendly and easy to understand.
Supports real-time multi-user connections and anonymous user access. by limiting the maximum number of users at the same time, the PC can run properly.

Outstanding security performance. You can set security measures at both the Directory and file levels. It provides different settings for different users and supports group management for a large number of users. Users can be granted or denied access permissions based on IP addresses.

Supports resumable upload during file upload and download.

Supports multiple host sites with multiple IP addresses.

You can set the upload/download ratio, hard disk space quota, and network bandwidth to ensure that your limited resources are not consumed by a large number of FTP users.

Can be used as the system service backend.

You can set the display information when a user logs on or exits, and support Unix-style external links.
The above list is only part of the Serv-U many functions. The specific usage will be described in detail below. What should I describe here? Serv-U provides a completely easy-to-use operation interface based on comprehensive and powerful functions. It can be said that everything is under control.
Instructions for use
All settings that users may encounter when using Serv-U can be implemented through the menu options in the Serv-U window. If you are installing Serv-U
Then, when Serv-U is started, the control window of Serv-U is not displayed on the screen. You can right-click Serv-U in the system tray of the task bar
Icon (an uppercase letter "U"), and then select the first "Show window" in the pop-up menu to display the control window of Serv-U.

Set up an FTP server

The first FTP-SERVER in the setup menu in the Serv-U control window is used
Server. The first "ftp port" in the window that appears after selection
Number is used to set the port number used by the FTP server. The FTP server listens to information of all visiting users through this port. In general, ftp
The default port number of the server is 21, but you can change it as needed, as long as the port number you use does not conflict with other network applications. Note that
Using the server port selected by the user can play a good role in security defense. At this time, only the user and other users who know the port number can successfully connect to the server. Therefore, we recommend that you
Use the selected port when setting the FTP server, instead of simply using the default value.
Then you need to set the maximum speed that the server can provide. Generally, you can
To leave this blank, the server will use all possible bandwidth to provide services to the customer. It is certainly good to provide users with the maximum access speed, but too many FTP
Users may eat away all possible bandwidth, making it almost impossible for other network applications. Therefore, it is important to properly control the maximum bandwidth occupied by the FTP server.
Next, set the maximum user access allowed by the server. Here, you can limit the maximum number of users who can access the FTP server within the same period of time. If this parameter is set to 0
The server rejects any user access requests. If this option is left blank, Serv-U will not control the number of visitors until all system resources are exhausted. If you want your FTP
If the server can maintain normal operation, it is best to limit the number of visiting users. Generally, even if the old 486
After Serv-U is used, the server can also provide access support for more than 20 users at the same time.
The first option in a series of subsequent retries is "enable security feature ". If
If this option is not selected, anyone can directly access FTP through the network
Server, which allows you to copy, modify, or even delete any files on the server. Except for those who have a small range of personal networks and do not want to repeatedly enter usernames, passwords, and other complicated procedures for each login
You must make sure that you have selected this option to enable the server security protection function.
Next "encrypt
Passwords is automatically selected by default. In this way, Serv-U will use
The same encryption mechanism of the operating system encrypts and saves the user's password. If you do not choose to encrypt the password, the passwords entered by all users will be stored in plain text in
Install the Serv-U.ini file under the directory.
The next item is used to set whether anonymous access users are required to enter the password. By default, this item is blank so that anonymous accounts are used.
Access FTP
The server user is not required to enter a password. It should be noted that the anonymous user password detection is very simple here, as long as the anonymous user enters any string that matches the email address format, Serv-U
It does not further determine whether the email address entered by the user actually exists.
The next item is anti-Timeout measures. If you select this option, Serv-U will adopt a new time recording method. users who want to regularly send commands to the server to prevent timeout will not succeed.
The subsequent options are used to determine whether to delete a file that has not been fully uploaded. If you do not use the delete function, when a user uploads a file to the FTP server but fails to complete the file upload, Serv-U retains the uploaded content on the hard disk, this enables resumable upload of uploaded files.
Next we will discuss cross-ftp attacks. Normally, when the FTP protocol is used for file transfer, the client first
The server issues a "Port" command, which contains the user's IP address and the port number that will be used for data transmission. After receiving the command, the server uses the user address information provided by the command to create
Establish a connection with the user. In most cases, the above process will not cause any problems. However, when the client is a malicious user
Add specific address information to the command to establish a connection between the FTP server and other non-client machines. Although this malicious user may not have the right to directly access a specific machine
If the server has the right to access this machine, then malicious users use ftp
As an intermediary, the server can still connect to the target server. This is the cross-server attack we mentioned. To prevent the above situation, you can select "prevent cross-FTP
Server attack option. In this way, before Serv-U establishes a connection with any visiting user, it must first check whether the address information provided by the user is the real address. Everything is in two ways. We already
We know that Serv-U can be used to prevent cross-FTP server attacks. However, we also abandoned
Data transmission between servers. This is because Serv-U
Only those users whose provided addresses are consistent with the actual addresses of the address provider will establish a connection. Users cannot remotely control file transfer between two different FTP servers.
The last two options are used to limit the maximum residence time of the user on the FTP server, and specify the case sensitivity of the file and directory names on the server.
Other related options in this window will be described in detail later.
User Account Management

The most basic task for a user to use an FTP server is to add and manage user information. Choose "users" from the "setup" menu to open Serv-U.
User Management window. This window can be divided into two parts. The window on the left shows all registered FTP Server users. Select any user, and the detailed configuration information will
It is displayed on the right of the window. If Serv-U is started for the first time, only one default account named "default" is displayed.
The following describes in detail the entire process of creating a new user account.
First, click the "new" button on the rightmost side of the window, and enter the username to be created in the pop-up window. At this time, the entered user name will appear in the user name column on the right of the window. You can also modify the account name in this column.
Then, you can enter the group name of the user group to which the account belongs or create a new group. Groups are concepts launched to facilitate the management of a large number of user groups. We can drag a large number of individual users
To different groups for unified management. Because users in the same group share some common attributes, such as user passwords and root directories, you only need to perform some operations on accounts with special attributes.
This greatly simplifies the management and maintenance of user accounts. Note that the special user account "anonymous" does not belong to any user group.
Enter the account password in the subsequent password column. If you select the password encryption option in the server settings (see the previous article ), the entered password is automatically stored in encrypted mode. Password heavy
One thing we need is that only the first eight characters in the input are valid, and we hope to cause a large number of Serv-U
Note. In addition, if the user did not enter the corresponding password when creating a new account, it does not mean that the user account has no password, Serv-U
You will try to find whether the user account belongs to a user group and the user group has a unified password. If Serv-U
If the user group password is not found, access to the user account is denied. If you do not want to specify the password for an account, you only need to enter "$ #@ 60; $" in the password field of the corresponding account.
# @ 60; none $ # @ 62; $ # @ 62. One exception to the above situation is the anonymous user account, which has no password, Serv-U
You only need to enter any string that meets the email address format.
In the "home" column, set the ftp
The root directory of the user, that is, the starting directory that the user automatically locates after successful logon. Each user account must have its own root directory; otherwise, Serv-U
Access to this user account is denied. Of course, if this account belongs to a group and the user group has already set a common root directory, you do not have to reset each account in the user group. The user is losing
When entering the address of the root directory, you must use the full path, including the drive letter.
In the "NOTE" column, you can enter some text to help you with your account for future reference.
The largest column on the right of the user window is used to set the account access permissions, so as to determine which files the user can access and how to access these files. Serv-U classifies user access permissions by file and directory. Specifically, it includes:

Access Permissions to files:

Read: allows users to download files;

Write: allows users to upload files, but does not have the right to modify, delete, or rename the files;

Append: allows you to attach existing files. Users with APPEND permissions automatically have the write

Permission;

Delete: allows users to modify, rename, or delete files. Users with the delete permission automatically

Write and append permissions;

Execute: allows you to run executable files through FTP. For example, you can remotely Run DOS or Windows

Program .

Access Permissions to directories:

List: allows users to obtain the directory list;

Make: allows you to create new subdirectories under the root directory;

Remove: allows you to delete subdirectories in the root directory.

Inherit: After this option is selected, the access permissions set for a directory are automatically assigned to all subdirectories in the directory.

Inheritance.

After completing all the preceding settings, click the "Store" button to save the newly created user account to the FTP server.

Other options in this window will be described in detail later.

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Real-time Monitoring

After completing the basic configuration of the FTP server, you can provide the FTP file transfer service to the outside world. I think many users want to provide FTP
In the process of service, you can monitor the users who access your server in real time. On the one hand, you can be aware of the entire service process, and on the other hand, before unexpected problems may occur, adoption and
Preventive and remedial measures. In this regard, we believe that Serv-U can fully meet your needs.
First, let's take a look at how to use Serv-U for real-time user monitoring.
Select the "User Info" option in the "file" menu. In the upper half of the window, all users currently connected to the server are displayed. If you click a user, the details of the user will appear in the lower half of the window.
There is a "spy on user" button in the lower right of the window. After you click it, the window that appears will display all commands sent by a specific user to the FTP server and responded to the FTP server. This window will track all the commands of the selected user and provide a reliable basis for understanding all the actions of a specific user when accessing the FTP server.
There is also a button named "Kill user" under this button. If a user finds that the behavior of a visitor is suspicious, it may cause harm to the normal operation of the FTP server, you can use this button to immediately interrupt the connection to the user and kick the user out of the FTP server.
Although Serv-U can provide real-time user monitoring information, it consumes a large part of system resources. If you find that the system performance drops significantly, you can use the "Freeze List" button on the right of the window to temporarily freeze the dynamic display of window information, so as to release valuable system resources.

Set server logging

In addition to Real-time Monitoring, Serv-U also provides powerful logging functions, allowing you to easily record and summarize the running status of Serv-U for a period of time.
Select "logging" under the "file" menu. The log settings window is displayed. You can select the events to record and where to save the record information.
On the right side of the window, you can choose to record different events, including system information and security information, at the same time, you can set whether to save the record in the main window that allows the upload ERV-u to a specified file. To consume system resources and backup information, we recommend that you save the log information to a specified file.

It must be noted that the log record file of Serv-U adopts a uniform format, as shown below:

[N] Date time-(XXXX) Message

The first number "N" indicates the type of the recorded information, which is:

N = 1: System Information (error information, etc );

N = 2: The FTP command issued by the user;

N = 3: File Download;

N = 4: File Upload;

N = 5: Security Information (user logon information, etc)

N = 6: FTP commands responded by the server;

N = 7: Winsock usage record;

N = 8: DLL file access records

In addition, "XXXX" in the brackets is a unique digital identifier that Serv-U assigns to each visitor.

5. Set logon and exit Information

Careful users may find that a window appears frequently when logging on to or exiting an FTP site, displaying information including system settings and welcome. So how can this function be implemented under Serv-U?
First, save the information to be displayed to the user in a text file, select "messages" in the "setup" menu, and set it in the pop-up window.
In the lower-down box at the top of the window, you need to select the IP address to use the logon and exit information. Because Serv-U supports multiple IP addresses on a machine, you need to select an IP address. In the following two options, enter the address of the text file that the user has already created, including logon and exit information.

Use external connection
External connections refer to connections that are displayed in a directory pointing to a file or directory outside the directory. In the user's opinion, the file or directory pointed to by the external connection is located under the current directory,
Actually, they are just some virtual pointers that act as connections. One of the biggest advantages of using external connections is the ability to centralize all the resources that the visitor may need into a directory, so that the user can
The external connection access is actually scattered information in different disks or directories.
To fully utilize the external connection function provided by Serv-U, you must first generate a text file to save all the external connections that may be used. The file format is as follows:

Link name | sourcename
The "Link name" is the name of the external connection displayed in the user's current directory, while the "sourcename" is the disk or directory to which the external connection actually points.
For example, we write the following information in a file named "link. txt:

CD-ROM | f: This will appear in the user's current directory "CD-ROM", click, you can directly access the FTP server Optical Drive.
After configuring the text file for external connections, select "FTP server" in the "ftle" menu and find "primary Fiel" in the pop-up window.
Containing link, and then enter the full path of the above text file. In "primary Fiel containing
There is a "secondary file ining" under Link
Link.

Set the upload/download Ratio

If users want their FTP site users to not only use their own resources, but also upload valuable things for sharing, you can use the "upload and download ratio" feature provided by Serv-U.
You can find the name U/d in the pop-up window for FTP-SERVER, users, and groups in the File menu
"Ratios" function button, click it to display the setting window. You can restrict each FTP
The number of files that a site user can download after uploading a file. For example, if you set the upload/download ratio of a user to 1/3, the user can
The website downloads three files.
Serv-U allows you to limit the proportion of uploaded and downloaded files based on the number of files transmitted or the size of files within a single session or all sessions.
Disk Quota

As the number of users increases, a very practical problem is how to ensure that each user has sufficient hard disk space available while preventing the FTP server from consuming the hard disk resources of the entire machine. Similarly, Serv-U provides a powerful solution to this problem.
You can find the function button "quato" in the "users" and "groups" options in the "file" menu. The setting window appears.
You can first check the hard disk space currently used by a user account, and then set the maximum disk space that different user accounts can control based on the actual situation, this effectively solves the problem of insufficient hard disk space.

Grant or deny access permissions based on IP addresses

Select the "IP Access" option in the "file" menu and set it in the pop-up window.
You can set different access rules on the left of the window, and all the current access rules will be displayed in the list on the right.
Serv-U
Two basic access rules are provided: "Access Denied" Rules and "Access Allowed" rules. Under the "Access Denied" rule, all visitors from IP addresses entered by users will be denied access.
Users from other IP addresses are granted access permissions. Similarly, if you select the "Allow access" rule, all visitors from IP addresses entered by the user will be granted access permissions
Users with its IP address will not have access to the FTP server.
With the above functions, users can set different permissions for different IP addresses, thus effectively protecting the FTP server from illegal access.
3. Section
Serv-U is a simple-to-use, powerful, easy-to-use FTP server software. I believe that the majority of users, combined with the above introduction and personal practices, will certainly build their own powerful FTP server in the shortest time.