NAME

     chroot — change root directory

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     int
     chroot(const char *dirname);

DESCRIPTION

     The dirname argument is the address of the pathname of a directory, terminated by an ASCII
     NUL.  The chroot() system call 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.

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

     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 always 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

RETURN VALUES

     Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and
     the global variable errno is set to indicate the error.

ERRORS

     The chroot() system call will fail and the root directory will be unchanged 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 translating the pathname.

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

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

SEE ALSO

     chdir(2), jail(2)

HISTORY

     The chroot() system call appeared in 4.2BSD.  It was marked as “legacy” in Version 2 of the
     Single UNIX Specification (“SUSv2”), and was removed in subsequent standards.

BUGS

     If the process is able to change its working directory to the target directory, 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.

SECURITY CONSIDERATIONS

     The system have many hardcoded paths to files where it may load after the process starts.
     It is generally recommended to drop privileges immediately after a successful chroot call,
     and restrict write access to a limited subtree of the chroot root, for instance, setup the
     sandbox so that the sandboxed user will have no write access to any well-known system
     directories.