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 8.1 April 18, 2001 NetBSD 8.1
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