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(10) File Permissions

File Permissions

UNIX is a multi-user system, (who | wc), file protection/access is required
Files have "permissions" (ls -l) that determine who has access to the files and what type of access, files also have an owner
File permissions are for USER (owner), GROUP, OTHER (public)
Need execute permission on a directory to "cd" in
(-rwxr-xr--) - User has read(r), write(w) and execute(x) permission. Group has read and execute, others have read only.
chmod ### file_name
Changes permissions, (AFS) is different. See www.dartmouth.edu/~rc/systems/AFS/afs.html. AFS uses Access Control Lists in combination with permissions. See fs_setacl
chmod can use symbolic settings (ugo+-=rwx) or numeric
numeric examples: chmod takes a three digit number and a file name as arguments, the first of the three digits indicates the file permission for the owner of the file, the second digit indicates permissions for the group and the third for the world
- chmod 755 - (-rwxr-xr-x)
- chmod 744 - (-rwxr--r--)
- chmod 000 - (----------)
symbolic examples:
- chmod u=rwx,go=rx - (-rwxr-xr-x)
- chmod u=rwx,go=r - (-rwxr--r--)
- chmod ugo-rwx - (----------)
chgrp
will change the group on the file, must be a member of the group changing to
chown
will change the owner of the file, must have permission to do this

slide10.src last modified Feb 8, 2011

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