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CHROOT(2)		    BSD	System Calls Manual		     CHROOT(2)

     chroot -- change root directory

     Standard C	Library	(libc, -lc)

     #include <unistd.h>

     chroot(const char *dirname);

     The dirname argument is the address of the	pathname of a directory, ter-
     minated by	an ASCII NUL.  The chroot() system call	causes dirname to be-
     come the root directory, that is, the starting point for path searches of
     pathnames beginning with `/'.

     In	order for a directory to become	the root directory a process must have
     execute (search) access for that directory.

     It	should be noted	that chroot() has no effect on the process's current

     This call is restricted to	the super-user.

     Depending on the setting of the `kern.chroot_allow_open_directories'
     sysctl variable, open filedescriptors which reference directories will
     make the chroot() fail as follows:

     If	`kern.chroot_allow_open_directories' is	set to zero, chroot() will al-
     ways fail with EPERM if there are any directories open.

     If	`kern.chroot_allow_open_directories' is	set to one (the	default),
     chroot() will fail	with EPERM if there are	any directories	open and the
     process is	already	subject	to the chroot()	system call.

     Any other value for `kern.chroot_allow_open_directories' will bypass the
     check for open directories

     Upon successful completion, a value of 0 is returned.  Otherwise, a value
     of	-1 is returned and errno is set	to indicate an error.

     The chroot() system call will fail	and the	root directory will be un-
     changed if:

     [ENOTDIR]		A component of the path	name is	not a directory.

     [EPERM]		The effective user ID is not the super-user, or	one or
			more filedescriptors are open directories.

     [ENAMETOOLONG]	A component of a pathname exceeded 255 characters, or
			an entire path name exceeded 1023 characters.

     [ENOENT]		The named directory does not exist.

     [EACCES]		Search permission is denied for	any component of the
			path name.

     [ELOOP]		Too many symbolic links	were encountered in translat-
			ing the	pathname.

     [EFAULT]		The dirname argument points outside the	process's al-
			located	address	space.

     [EIO]		An I/O error occurred while reading from or writing to
			the file system.

     chdir(2), jail(2)

     The chroot() system call appeared in 4.2BSD.

     If	the process is able to change its working directory to the target di-
     rectory, but another access control check fails (such as a	check for open
     directories, or a MAC check), it is possible that this system call	may
     return an error, with the working directory of the	process	left changed.

BSD				 June 4, 1993				   BSD


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