chroot(2) - NetBSD Manual Pages

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CHROOT(2)                 NetBSD Programmer's Manual                 CHROOT(2)


NAME

     chroot - change root directory


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <unistd.h>

     int
     chroot(const char *dirname);

     int
     fchroot(int fd);


DESCRIPTION

     dirname is the address of the pathname of a directory, terminated by an
     ASCII NUL.  chroot() causes dirname to become 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.

     If the current working directory is not at or under the new root directo-
     ry, it is silently set to the new root directory.  It should be noted
     that, on most other systems, chroot() has no effect on the process's cur-
     rent directory.

     This call is restricted to the super-user.

     The fchroot() function performs the same operation on an open directory
     file known by the file descriptor fd.


RETURN VALUES

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


ERRORS

     chroot() will fail and the root directory will be unchanged if:

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

     [ENAMETOOLONG]
                   A component of a pathname exceeded {NAME_MAX} characters,
                   or an entire path name exceeded {PATH_MAX} 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 translating the
                   pathname.

     [EFAULT]      dirname points outside the process's allocated address
                   space.

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

     fchroot() will fail and the root directory will be unchanged if:

     [EACCES]      Search permission is denied for the directory referenced by
                   the file descriptor.

     [EBADF]       The argument fd is not a valid file descriptor.

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

     [ENOTDIR]     The argument fd does not reference a directory.


SEE ALSO

     chdir(2)


HISTORY

     The chroot() function call appeared in 4.2BSD.  Working directory han-
     dling was changed in NetBSD 1.4 to prevent one way a process could use a
     second chroot() call to a different directory to "escape" from the re-
     stricted subtree.  The fchroot() function appeared in NetBSD 1.4.

NetBSD 1.5.1                    April 18, 2001                               2