chroot - 改变根目录
int chroot(const char *path);
Only a privileged process (Linux: one with the CAP_SYS_CHROOT capability) may callchroot(2).This call changes an ingredient in the pathname resolution process and does nothing else.
This call does not change the current working directory, so that after the call ‘.’ can be outside the tree rooted at ‘/’. In particular, the superuser can escape from a ‘chroot jail’ by doing ‘mkdir foo; chroot foo; cd ..’.
This call does not close open file descriptors, and such file descriptors may allow access to files outside the chroot tree.
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
Depending on the file system, other errors can be returned. The more general errors are listed below:
|EACCES||Search permission is denied on a component of the path prefix. (See also path_resolution(2).)|
|EFAULT||path points outside your accessible address space.|
|EIO||An I/O error occurred.|
|ELOOP||Too many symbolic links were encountered in resolving path.|
|ENAMETOOLONG||path is too long.|
|ENOENT||The file does not exist.|
|ENOMEM||Insufficient kernel memory was available.|
|ENOTDIR||A component of path is not a directory.|
|EPERM||The caller has insufficient privilege.|
SVr4, 4.4BSD, SUSv2 (marked LEGACY). This function is not part of POSIX.1-2001.
A child process created via fork(2) inherits its parent’s root directory. The root directory is left unchanged by execve(2).
FreeBSD has a stronger jail() system call.