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28 .\" @(#)chroot.2 8.1 (Berkeley) 6/4/93
36 .Nd change root directory
42 .Fn chroot "const char *dirname"
47 is the address of the pathname of a directory, terminated by an ASCII NUL.
52 to become the root directory,
53 that is, the starting point for path searches of pathnames
57 In order for a directory to become the root directory
58 a process must have execute (search) access for that directory.
60 It should be noted that
62 has no effect on the process's current directory.
64 This call is restricted to the super-user.
66 Depending on the setting of the
67 .Ql kern.chroot_allow_open_directories
68 sysctl variable, open filedescriptors which reference directories
74 .Ql kern.chroot_allow_open_directories
79 if there are any directories open.
82 .Ql kern.chroot_allow_open_directories
83 is set to one (the default),
87 if there are any directories open and the
88 process is already subject to the
93 .Ql kern.chroot_allow_open_directories
94 will bypass the check for open directories
101 will fail and the root directory will be unchanged if:
104 A component of the path name is not a directory.
106 The effective user ID is not the super-user, or one or more
107 filedescriptors are open directories.
108 .It Bq Er ENAMETOOLONG
109 A component of a pathname exceeded 255 characters,
110 or an entire path name exceeded 1023 characters.
112 The named directory does not exist.
114 Search permission is denied for any component of the path name.
116 Too many symbolic links were encountered in translating the pathname.
121 points outside the process's allocated address space.
123 An I/O error occurred while reading from or writing to the file system.
131 system call appeared in
137 and was removed in subsequent standards.
139 If the process is able to change its working directory to the target
140 directory, but another access control check fails (such as a check for
141 open directories, or a MAC check), it is possible that this system
142 call may return an error, with the working directory of the process
144 .Sh SECURITY CONSIDERATIONS
145 The system have many hardcoded paths to files where it may load after
147 It is generally recommended to drop privileges immediately after a
151 and restrict write access to a limited subtree of the
155 setup the sandbox so that the sandboxed user will have no write
156 access to any well-known system directories.