chroot(2) - NetBSD Manual Pages

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CHROOT(2)                 NetBSD System Calls 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 direc-
     tory, 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} charac-
                        ters, or an entire path name exceeded {PATH_MAX} char-
                        acters.

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

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

     [EPERM]            The effective user ID of the calling process is not
                        the super-user.

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

     [EACCES]           Search permission is denied for the directory refer-
                        enced 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.

     [EPERM]            The effective user ID of the calling process is not
                        the super-user.


SEE ALSO

     chdir(2)


STANDARDS

     The chroot() function conforms to X/Open System Interfaces and Headers
     Issue 5 (``XSH5''), with the restriction that the calling process' work-
     ing directory must be at or under the new root directory.  Otherwise, the
     working directory is silently set to the new root directory; this is an
     extension to the standard.

     chroot() was declared a legacy interface, and subsequently removed in
     IEEE Std 1003.1-2001 (``POSIX.1'').


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
     restricted subtree.  The fchroot() function appeared in NetBSD 1.4.

NetBSD 5.2                      April 18, 2001                      NetBSD 5.2