Nếu các chính sách dự kiến các thời điểm cụ thể trong ngày, xảy ra luôn luôn ở cùng một thời gian trong ngày, hoặc ít lần thay đổi, có lẽ ngẫu nhiên. Quyết định này ảnh hưởng đến khả năng dự báo của hệ thống, và do đó có thể bảo mật của nó trong một cuộc gặp gỡ thù địch. | 376 CHAPTER 9. APPLICATION-LEVEL SERVICES share -F nfs -o rw hostlist root starfleet iu mercury u2 share -F nfs -o rw hostlist root starfleet iu mercury u3 share -F nfs -o rw hostlist root starfleet iu mercury u4 share -F nfs -o rw hostlist var mail This script exports the six named filesystems read-write to the entire list of hosts named in the variable hostlist. The command shareall runs this script or it can be run manually by typing sh etc dfs dfstab. The command share without arguments shows the currently exported filesystems. Notice that the hostname daystrom is repeated once unqualified and again with a fully qualified hostname. This is sometimes necessary in order to make the entry recognized. The mount daemon is not particularly intelligent when it verifies hostnames. Some systems send the fully qualified name to verify and others send the unqualified name. If in doubt list both like this. Client-side mounting Clients may mount any subdirectory of the exported directory onto any local directory by becoming root and either executing a shell command of the form mount server remote-directory local-directory or by adding a line to the filesystem table file usually called etc fstab. On some brands of Unix this file has been renamed as etc checklist or etc filesystems. On Solaris systems it is called etc vfstab. The advantage of writing the disks in the filesystem table is that the mount commands will not be lost when we reboot our system. The filesystems in the filesystem table file are mounted automatically when the system is booted. All the file systems in this file are mounted with the simple command mount -a. We begin by looking at the manual page on the appropriate file for the system or better still looking at examples which are already in the file. The form of a typical filesystem table is as dev sda2 swap swap rw bg 1 1 dev sda1 ext2 rw bg 1 1 dev sda3 iu borg local ext2 rw bg 1 1 mercury iu mercury u1 iu mercury u1 nfs rw bg mercury iu .
