Mode Bits

• Ignored for directories

• For files, group and other mode bits ignored

• R mode bit must be set to read a file

• R and X bits must be set to execute a file

• W bit must be set to write to or delete a file

• Suid and sgid may not do what you expect

In Coda, the Unix mode bits on directories are ignored. On files, the group and other mode bits are ignored; only the user bits have any effect. To read a file you need read and lookup access to the directory through its ACLs, and the file needs its R mode bit set. (While other Unix file systems allow you to read files in `hidden' directories if you know their names, Coda does not.)

To execute a file, you need read and lookup ACLs, and you need both R and X mode bits set. (While some other Unix file systems allow you to execute a file which you cannot read, Coda does not.) And you cannot write or delete a file unless its W bit is set.

Coda remembers the Coda user ID of a file, the ID of the Coda user who created it. But the owner and group of a file have no influence on who can access it. The Coda system administrator can make an executable file in Coda SUID, in which case the command gets the effective Unix user ID of the file owner. Note that this does not give the program the access which that Coda user has; it does not give a running SUID program an effective Coda ID. This may cause problems if you want cron jobs to write into Coda.

All files and directories in Coda appear to have the Unix group `nogroup', so SGID programs are not useful.