4.9 Restricted Shells

Restricted shells can be invoked in any of the following ways:

rksh
	

Korn shell

 
ksh -r
 
set -r
  
rsh
	

Bourne Shell

 
set -r

Restricted shells can also be set up by supplying rksh and rsh in the shell field of /etc/passwd or by using them as the value for the SHELL variable.

Restricted shells act the same as their non-restricted counterparts, except that the following are prohibited:

• Changing directory (i.e., using cd ).

• Setting the PATH variable. rksh also prohibits setting ENV and SHELL.

• Specifying a / for command names or pathnames.

• Redirecting output (i.e., using > and >> ).

Shell scripts can still be run, since in that case the restricted shell will call ksh or sh to run the script.