Hey there! Let’s break down what those uid and gid parameters do when mounting CIFS shares via /etc/fstab—I’ve tinkered with this setup plenty, so I’ll keep it clear and practical.

First, remember that CIFS (the protocol for Windows file shares) doesn’t use Linux’s user/group ID system natively. When you mount a CIFS share on Linux, you need to bridge that gap, and uid/gid are the basic way to do it:

• uid (User ID): This sets the default owner user ID for every file and directory in the mounted CIFS share, from Linux’s perspective. For example, if you set uid=1000, every user on your Linux system will see all files in the share as owned by the user with UID 1000 (usually your main regular user). When any Linux user reads/writes to the share, they’re effectively acting as that UID when interacting with the CIFS server.
• gid (Group ID): This works the same way, but for user groups. All files in the mounted share will show as belonging to the group with the specified GID, regardless of which Linux user is accessing them.

The reason these parameters apply to all users is that this is a global permission mapping. CIFS doesn’t support per-Linux-user identity out of the box with basic mounts, so uid/gid creates a one-size-fits-all identity for anyone accessing the share.

These two parameters aren’t exclusive to CIFS—they’re useful for any file system that doesn’t natively store Linux-style user/group metadata:

• Non-Linux file systems: For filesystems like VFAT, NTFS, or CIFS, which don’t track Linux UIDs/GIDs, uid/gid lets you assign a consistent owner/group so Linux can enforce permissions correctly.
• Unified access: If you want all users on your system to interact with a mounted drive (like a USB stick or network share) using the same permission set, setting uid/gid ensures no one runs into "permission denied" errors because of mismatched ownership.
• Simplified management: Instead of manually chowning files after mounting, uid/gid sets ownership automatically at mount time, saving you extra steps.

Quick Example #

Here’s how a typical CIFS line in /etc/fstab might look with these parameters:

//your-windows-server/share-name /mnt/cifs-share cifs uid=1000,gid=1000,username=your-win-user,password=your-win-pass 0 0

In this case, every file in /mnt/cifs-share will show up as owned by UID 1000 and GID 1000, no matter which Linux user accesses it.

A quick side note: If you need per-user access controls for CIFS, you can look into the multiuser mount option paired with the cifscreds tool—but that’s a more advanced setup. The global uid/gid is the go-to for simple, shared access.

内容的提问来源于stack exchange，提问作者Asqiir