Linux文件系统中'others'权限组是什么？是否必需？仅user和group可行吗？

Alright, let's walk through your questions step by step—this is a great set of questions that get to the core of how Linux's permission model works.

1. What exactly does the 'others' permission group refer to? #

In Linux's standard permission model, every file/directory has three distinct permission sets:

• user: Permissions granted exclusively to the owner of the file (you can spot this in ls -l output as the first trio of permission bits).
• group: Permissions for any user who is a member of the file's assigned group.
• others: This is the "everyone else" bucket—it covers every user on the system who is neither the file's owner nor part of the file's group.

For example: If a file is owned by lisa and assigned to the design group, a user tom who isn't lisa and isn't in the design group will be governed by the others permissions when interacting with that file.

2. Is 'others' a required part of file permission configuration? #

Absolutely—it's a mandatory component of Linux's base permission system. The permission structure for files/directories is hardcoded as three sets of three bits (read/write/execute) — one for user, one for group, one for others. You can't remove the 'others' set entirely; even if you lock it down to --- (no access at all), the field still exists in the permission metadata. It's a fundamental part of how the OS evaluates access rights.

3. Can 'user' and 'group' alone cover all file read/write/execute needs? #

Nope, they can't. Here are a few key scenarios where 'others' is essential, or where relying only on user/group would break functionality:

• System-wide tools: Files like /bin/ls or /usr/bin/git need to be executable by every user on the system. Without granting execute permissions to 'others', only the owner (usually root) and members of the file's system group could run these tools—making the system unusable for regular users.
• Public shared spaces: Directories like /tmp are designed for temporary file storage accessible to all users. You need 'others' set to rwx here so any user can create, read, and manage their own temporary files.
• Broad read access: Suppose you have a documentation file that you want any user to read (but not edit), regardless of their group. Setting 'others' to r-- is the simple, straightforward way to do this—you don't want to add every user on the system to a specific group just for this single file.

That said, if you need more granular control than the three permission sets allow (e.g., giving access to one specific non-owner/non-group user without opening it to everyone), you'd use ACLs (Access Control Lists) to extend the base model. But for the standard permission system, 'others' is a critical, non-negotiable piece.

内容的提问来源于stack exchange，提问作者Prem