APLawrence.com -  Resources for Unix and Linux Systems, Bloggers and the self-employed

2004/09/13 acl

© September 2004 Tony Lawrence

Access Control List. Basically, extended permissions. Some modern Unixes (Linux, UW, and others) have extended the permissions model. This requires new commands beyond chmod, and may be limited to certain types of filesystems. For example, on Red Hat Linux 7, the "chattr +i file" command makes "file" unchangeable and not able to be deleted: "immutable", even by its owner (the owner can, of course, "chattr -i file" to undo this). This can really help in preventing accidental removal of files, but it can be very confusing for users who aren't even aware that such attributes exist. Mac OS X and BSD systems add a "system immutable" bit, which, once set, can only be undone in single user mode. That effectively prevents changes even if the attacker has somehow already gained root (assuming that they are unable to bring the machine to single user mode). On other Unixes, these types of things may be handled by "setacl" commands; check your man pages for details. Sometimes there can be multiple levels: Mac has both chflags and SetFile, which do different things.

Got something to add? Send me email.

(OLDER)    <- More Stuff -> (NEWER)    (NEWEST)   

Printer Friendly Version

-> acl

Inexpensive and informative Apple related e-books:

Take Control of Preview

Take Control of Numbers

Photos: A Take Control Crash Course

Take Control of Parallels Desktop 12

Take Control of High Sierra

More Articles by © Tony Lawrence

Printer Friendly Version

Have you tried Searching this site?

This is a Unix/Linux resource website. It contains technical articles about Unix, Linux and general computing related subjects, opinion, news, help files, how-to's, tutorials and more.

Contact us

Printer Friendly Version

An editor is a person who knows precisely what he wants, but isn't quite sure. (Walter Davenport)

Linux posts

Troubleshooting posts

This post tagged:




Unix/Linux Consultants

Skills Tests

Unix/Linux Book Reviews

My Unix/Linux Troubleshooting Book

This site runs on Linode