How to Set an ACL on a File

1. Set an ACL on a file by using the setfacl command.

   $ setfacl -s user::perms,group::perms,other:perms,mask:perms,acl-entry-list filename ...

   -s	Sets an ACL on the file. If a file already has an ACL, it is replaced. This option requires at least the file owner, file group, and other entries.
   user::perms	Specifies the file owner permissions.
   group::perms	Specifies the file group permissions.
   other:perms	Specifies the permissions for users other than the file owner or members of the file group.
   mask:perms	Specifies the permissions for the ACL mask. The mask indicates the maximum permissions that are allowed for users (other than the owner) and for groups.
   acl-entry-list	Specifies the list of one or more ACL entries to set for specific users and groups on the file or directory. You can also set default ACL entries on a directory. Table 15–8 and Table 15–9 show the valid ACL entries.
   filename ...	Specifies one or more files or directories on which to set the ACL, separated by a space.

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   Caution –

   If an ACL already exists on the file, the -s option will replace the entire ACL with the new ACL.

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   For more information, see setfacl(1).

2. Verify that an ACL was set on the file or verify which ACL entries were set on the file.

   $ getfacl filename

   For more information, see How to Check If a File Has an ACL.

Examples—Setting an ACL on a File

In the following example, the file owner permissions are set to read and write, file group permissions are set to read only, and other permissions are set to none on the ch1.doc file. In addition, the user george is given read and write permissions on the file, and the ACL mask permissions are set to read and write, which means that no user or group can have execute permissions.

$ setfacl -s user::rw-,group::r--,other:---,mask:rw-,user:george:rw- ch1.doc
$ ls -l
total 124
-rw-r-----+  1 nathan  sysadmin   34816 Nov 11 14:16 ch1.doc
-rw-r--r--   1 nathan  sysadmin   20167 Nov 11 14:16 ch2.doc
-rw-r--r--   1 nathan  sysadmin    8192 Nov 11 14:16 notes
$ getfacl ch1.doc
# file: ch1.doc
# owner: nathan
# group: sysadmin
user::rw-
user:george:rw-    #effective:rw-
group::r--         #effective:r--
mask:rw-
other:---

In the following example, the file owner permissions are set to read, write, and execute, file group permissions are set to read only, other permissions are set to none, and the ACL mask permissions are set to read on the ch2.doc file. In addition, the user george is given read and write permissions. However, due to the ACL mask, the permissions for george are read only.

$ setfacl -s u::7,g::4,o:0,m:4,u:george:7 ch2.doc
$ getfacl ch2.doc
# file: ch2.doc
# owner: nathan
# group: sysadmin
user::rwx
user:george:rwx         #effective:r--
group::r--              #effective:r--
mask:r--
other:---