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Linux Interview Questions

ACL Permissions

1. What is ACL in Linux?
A) ACL (Access Control List) provides fine-grained permissions beyond standard rwx for owner, group, and others.
It allows setting permissions for multiple users or groups.

2. How do you view ACLs of a file?
A)

getfacl filename

3. How do you set an ACL for a specific user on a file?
A)

setfacl -m u:username:rwx file.txt

4.How do you set an ACL for a group?
A)

setfacl -m g:developers:rw file.txt

5.What is the difference between standard permissions and ACL?
A)

  • Standard permissions → only owner, group, others.
  • ACL → allows multiple users and groups with different permissions.

6.How do you remove an ACL entry?
A)

setfacl -x u:username file.txt

7.How do you remove all ACLs from a file?
A)

setfacl -b file.txt

8. If a file has both ACL and standard permissions, which takes precedence?
A) ACL permissions override standard permissions.

9.What happens if you delete a user who has ACL permissions?
A)The ACL entry remains but becomes ineffective until reassigned.

10.What is the difference between file permission and access control list (ACL)?
A)

  • File permission → basic rwx for owner, group, others.
  • ACL → fine-grained permissions for multiple users/groups.

11.A developer complains they don’t have write access to a shared directory, but the group has write permission. What could be the reason?
A) An ACL mask might be restricting effective permissions. Use:

getfacl shared_dir

and check the mask entry.

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