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Name

chroot, fchroot - change root directory

Synopsis

#include <unistd.h>

int chroot(const char *path);

int fchroot(int fildes);

Description

chroot() and fchroot() cause a directory to become the root directory, the starting point for path searches for path names beginning with /. The user’s working directory is unaffected by the chroot() and fchroot() functions.

path points to a path name naming a directory. The fildes argument to fchroot() is the open file descriptor of the directory which is to become the root.

The effective user ID of the process must be super-user to change the root directory. fchroot() is further restricted in that while it is always possible to change to the system root using this call, it is not guaranteed to succeed in any other case, even should fildes be valid in all respects.

The ‘‘..’’ entry in the root directory is interpreted to mean the root directory itself. Thus, ‘‘..’’ cannot be used to access files outside the subtree rooted at the root directory. Instead, fchroot() can be used to set the root back to a directory which was opened before the root directory was changed.

Return Values

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

Errors

chroot() will fail and the root directory will remain unchanged if one or more of the following are true:

EACCES
Search permission is denied for a component of the path prefix of dirname.
Search permission is denied for the directory referred to by
dirname.
EBADF
The descriptor is not valid.
EFAULT
path points to an illegal address.
EINVAL
fchroot() attempted to change to a directory which is not the system root and external circumstances do not allow this.
EINTR
A signal was caught during the chroot() function.
EIO
An I/O error occurred while reading from or writing to the file system.
ELOOP
Too many symbolic links were encountered in translating path.
EMULTIHOP
Components of path require hopping to multiple remote machines and file system type does not allow it.
ENAMETOOLONG
The length of the path argument exceeds {PATH_MAX}, or the length of a path component exceeds {NAME_MAX} while {_POSIX_NO_TRUNC} is in effect.
ENOENT
The named directory does not exist or is a null pathname.
ENOLINK
path points to a remote machine and the link to that machine is no longer active.
ENOTDIR
Any component of the path name is not a directory.
EPERM
The effective user of the calling process is not super-user.

See Also

chroot(1M) , chdir(2)

Warnings

The only use of fchroot() that is appropriate is to change back to the system root.

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