Friday, February 15, 2013

Special permissions on files and directories: SetUID, SetGID and Sticky bit.

Special Permissions

























Special permissions on files and directories: SetUID, SetGID and Sticky bit.
Special Permissionson a Fileon a Directory
SUID or Set User IDA program is executed with the file owner's permissions (rather than with the permissions of the user who executes it).Files created in the directory inherit its UID.
SGID or Set Group IDThe effective group of an executing program is the file owner group.Files created in the directory inherit its GID.
Sticky (bit)A program sticks in memory after execution.Any user can create files, but only the owner of a file can delete it.


































Permissions as output in columns 2 to 10 of
ls -l and their meaning.
PermissionsMeaning
--S------SUID is set, but user (owner) execute is not set.
--s------SUID and user execute are both set.
-----S---SGID is set, but group execute is not set.
-----s---SGID and group execute are both set.
--------TSticky bit is set, bot other execute is not set.
--------tSticky bit and other execute are both set.

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