File permissions

TODO

On this Page

• Viewing and modifying file permissions

The storage on Aoraki uses 2 systems of file permissioning.

Location	Unix permissions	ACL Permissions
/home/<username>
/projects
/weka

Unix Permissions

Unix file permissions control who can read, write, or execute a file or directory. They apply to three categories:

• Owner – the user who owns the file
• Group – users in the file's group
• Others – all other users

📜 Permission Types

Symbol	Meaning
r	Read
w	Write
x	Execute
-	No permission

For example, given -rwxr-xr-- the permissions would be:

• Owner rwx Read, write, execute
• Group r-x Read, execute only
• Others r-- Read only

To view or change the Unix permissions on a file

Terminal

# View permissions
ls -l filename

Modifying permissions with chmod

TODO

Access Control Lists (ACL)

ACLs extend the standard Unix file permission model (owner/group/others) by allowing fine-grained access control for additional users and groups on a per-file or per-directory basis.

Where the standard permissions (chmod) set access for:

• Owner
• Group
• Others

ACLs allow for:

• Specific users (e.g., user:bob)
• Specific groups (e.g., group:research)
• Default rules for directories (e.g., default:user:bob)

NFSv4 ACL Breakdown Each line has the form:

bash Copy Edit A:(type):[who]:permissions Where:

A = allow (you might also see D = deny)

OWNER@, GROUP@, EVERYONE@ = NFSv4 built-in identities

u:username@domain = specific user

g:group@domain = specific group

Code	Name	What it allows
r	Read Data	Read file contents or list directory contents
w	Write Data	Modify file contents or create files in a directory
a	Append Data	Append to a file or create subdirectories in a directory
D	Delete Child	Delete files within a directory
x	Execute	Execute file or traverse directory
t	Read Attributes	View basic file metadata (size, timestamps)
T	Write Attributes	Modify basic file metadata (e.g. change timestamps)
n	Read Named Attributes	Access extended attributes
N	Write Named Attributes	Modify extended attributes
c	Read ACL	View the ACL of the file
C	Write ACL	Modify the ACL of the file
y	Synchronize	Ensure file changes are written to stable storage (fsync)

Example

Terminal

nfs4_getfacl /projects/

# file: /projects/
A::OWNER@:rwaDxtTnNcCy
A::GROUP@:rxtncy
A::EVERYONE@:rxtncy

NFSv4 ACL Entries Explained

Entry	Who it applies to	Permissions	Meaning
A::OWNER@:rwaDxtTnNcCy	File owner	rwaDxtTnNcCy	Full access
A::GROUP@:rxtncy	File group	rxtncy	Read + Execute + Metadata access
A::EVERYONE@:rxtncy	Everyone else	rxtncy	Read + Execute + Metadata access

What's next?