Filesystem Permissions and ACLs Flashcards
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Read the first 7 Filesystem Permissions and ACLs flashcards as text
A user's umask is 027. What permissions will a newly created regular file have?
Answer: 640
Files start at 666 max; 666 minus umask 027 gives 640 (rw-r-----) for regular files.
What does 'setfacl -d -m g:developers:rwx projectdir' accomplish?
Answer: Sets a default ACL so new files in projectdir inherit rwx for the developers group
The -d flag sets a default ACL entry that is automatically inherited by new files and subdirectories created inside the directory.
Which ls option shows a '+' indicator next to files that have extended ACLs?
Answer: ls -l
ls -l displays a '+' at the end of the permission string for any file or directory that has an extended ACL beyond the standard POSIX permissions.
A script has permissions '-rwsr-xr-x' and is owned by root. What happens when a normal user runs it?
Answer: It runs with root privileges due to the setuid bit
The setuid bit (s in the owner execute position) causes the process to run with the file owner's (root's) effective UID.
How do you copy a file's ACL from 'source.txt' to 'dest.txt'?
Answer: getfacl source.txt | setfacl --set-file=- dest.txt
Piping getfacl output into setfacl --set-file=- is the standard way to copy ACL entries between files.
Which permission allows a user to traverse (enter) a directory without reading its contents?
Answer: Execute (x)
The execute bit on a directory controls the ability to cd into it and access files within it by name, independent of read permission.
A file is owned by 'alice' with permissions '640'. User 'bob' is in the same group. What can bob do?
Answer: Read the file only
640 means rw-r-----, giving the group (which includes bob) read-only permission.
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