File sharing is one of the most commonly used features in Windows Server. It allows team members to access unified file resources across devices and departments, significantly improving collaboration efficiency. However, in practice, "file share inaccessibility" is almost always one of the most common issues administrators encounter. Users may see messages such as "Cannot access this share," "Access denied," or "Network path not found." These issues may seem complex, but they are essentially closely related to permission settings, network protocols, and authentication.

　　I. Basic Principles of Windows File Sharing

　　Windows file sharing is based on the SMB protocol, which allows clients to access resources such as files, printers, and named pipes on a server over the network. Common access methods include:

　　Direct access through Explorer: \\ServerName\ShareName

　　Mapping a network drive: Mounting a shared folder as a local disk (such as drive Z:).

　　Behind the scenes, SMB establishes a connection over TCP port 445, uses NTLM or Kerberos for authentication, and then implements access control based on file system permissions (NTFS permissions) and share permissions.

　　II. Permission System Analysis: Share Permissions vs. NTFS Permissions

　　Many administrators, when configuring a share for the first time, only adjust the "share permissions" but overlook the NTFS file system permissions, which often results in access denied. To understand file share permissions, it's important to first distinguish between the two:

　　1. Share Permissions: These permissions, configured in the "Share Settings" interface, control the level of access network users have to shared resources. There are three main types:

• Read: Only able to view files;
• Change: Can modify, create, and delete files;
• Full Control: Allows all operations, including changing share settings.

　　Share permissions apply to users accessing the file over the network, not to local users.

　　2. NTFS Permissions (File System Permissions)

　　These are local permissions for folders at the NTFS file system level. They define the specific permissions a user or group can have on the file on the local system, such as read, write, modify, and delete.

　　NTFS permissions are more granular, with examples including Read & Execute, List Folder Contents, Modify, and Full Control.

　　3. Permission Merging Principle

　　When Windows processes a share access request, it checks both the share permissions and the NTFS permissions. The most restrictive (lowest) of the two permissions is the one that takes effect.

　　For example, if the share permission is "Full Control" but the NTFS permission only allows "Read," the end user will only be able to "Read."

　　Therefore, when configuring a share, it is recommended to set the share permission to "Everyone: Full Control." NTFS controls the actual permissions, enabling precise security management.

　　III. Common Reasons for File Share Access Failure

　　There are many reasons for file share access failure, which can generally be categorized as follows:

　　1. Network connectivity issues: For example, the client cannot resolve the server name, TCP ports 445 or 139 are blocked by a firewall, the network is isolated, or the subnet is disconnected.

　　2. Permission misconfiguration: For example, NTFS or share permissions are incorrectly assigned, the accessor account is not included in the authorized group, or anonymous access is disabled.

　　3. Authentication failure: For example, conflicts between domain and local user permissions, incorrect account passwords or cached credentials, and SMB version compatibility issues.

　　4. Services are not enabled or configured correctly: For example, the "Server" or "Workstation" service is not started, the file sharing protocol component is not installed, or the firewall policy does not allow file sharing.

　　IV. Troubleshooting Steps and Solutions

　　1. Verify network connectivity

　　Use the command on the client:

ping ServerName

　　If the host name cannot be resolved, try accessing it directly using the IP address:

\\192.168.1.10\ShareName

　　If you can access it, the problem lies with DNS resolution. You can add a temporary resolution in the hosts file or check the domain's DNS records.

　　Also, use:

telnet ServerIP 445

　　Test whether the SMB port is open. If the connection fails, check the Windows Firewall settings to ensure that the "File and Printer Sharing" rule is enabled.

　　2. Check service status

　　File sharing relies on the following key services: Server, Workstation, TCP/IP NetBIOS Helper, and Computer Browser (older version).

　　You can check this using the command:

sc query lanmanserver

　　If not running:

net start lanmanserver

　　Also ensure that the SMB protocol feature is enabled (Windows Server 2016+):

Get-WindowsFeature FS-SMB1, FS-SMB2

　　If necessary, enable it via PowerShell:

Enable-WindowsOptionalFeature -Online -FeatureName "SMB1Protocol"

　　However, in modern environments, SMB2/3 should be used first to improve security.

　　3. Check share settings and security permissions

　　(1) Confirm whether the share exists

　　Execute on the server:

net share

　　Confirm the share name and path. If missing, you can recreate it:

net share Documents=C:\Shared /grant:Everyone,full

　　(2) Check NTFS permissions

　　Right-click the shared folder → "Properties" → "Security" → View user group permissions.

　　Common configuration suggestions:

　　Administrators: Full control;

　　Specified user groups (such as "Finance Department"): Modify permissions;

　　Other users: Read only or deny access.

　　Avoid deleting the system default "Everyone" or "Authenticated Users" entries, otherwise the share may become completely inaccessible.

　　4. Verify user identity and access credentials

　　When accessing from the client, Windows may cache old credentials, which can be cleared using the command:

cmdkey /list
cmdkey /delete:ServerName

　　Then reconnect:

net use \\ServerName\ShareName /user:Domain\User password

　　If the server is in a domain environment, domain accounts should be used for access. If it is in a workgroup environment, ensure that the client account matches the local account on the server (with the same username and password).

　　5. Check Group Policy and Security Policy

　　In some environments, system policies prohibit anonymous access or network logons. This can be checked by going to: Local Security Policy → Local Policies → User Rights Assignment.

• Allowed users or groups should be included in "Access this computer from the network."
• Do not mistakenly include regular users in "Deny access to this computer from the network."

　　Additionally, in Security Options, check the following:

• "Network access: Do not allow anonymous enumeration of SAM accounts and shares";
• "Network security: LAN Manager authentication level";

　　These policies may prevent older systems or non-domain computers from accessing shares.

　　6. SMB Version Compatibility Issues

　　Newer versions of Windows Server disable SMB1 by default, while older systems (such as Windows 7 or XP) may only support SMB1. If compatibility is required, you can temporarily enable:

Enable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol

　　However, due to the serious security risks of SMB1, it's recommended to use SMB2 or upgrade the client system.

　　File share inaccessibility may appear to be a simple "permissions issue," but it actually involves multiple layers, including network, authentication, policy, and protocol issues. Troubleshooting should follow this sequence: network connectivity → service status → permission configuration → credential verification → policy and protocol compatibility. Only by mastering this logic can you effectively resolve the issue. In an enterprise environment, good permission planning and standardized sharing policies are far more important than temporary fixes. By properly configuring NTFS permissions, using domain accounts for unified management, and enabling SMB encryption and log auditing, you can ensure stable and secure Windows Server file sharing.