Managing NFS and NIS, 2nd Edition - Mike Eisler [116]
# Directory Map NFS Mount Options
/tools /etc/auto_tools -ro
/- /etc/auto_direct
The first entry is for the indirect map /etc/auto_tools; entries in this map are mounted read-only (due to the -ro option) under the /tools directory. The second line of the master file is for a direct map; because there is no directory for the automounter to manage, the place holder /- is used. Note that the master map format is different from other automounter maps in the following ways:
With the master maps, the mount options are in the third column, whereas regular automounter maps place the options in the second column.
The first column in a master map is always an absolute pathname that starts with a leading slash (/) and can have one or more additional slashes, whereas with indirect maps the first column is a map key that must not contain a slash.
The earlier example is somewhat limiting in that changes to the auto_tools or auto_direct map must be made by editing each /etc/auto_tools or /etc/auto_direct file on each NFS client. Instead, if we drop the /etc/ prefix, we can allow the maps to be maintained in NIS or files:
# Directory Map NFS Mount Options
/tools auto_tools -ro
/- auto_direct
In this example, we observe three things:
Two map names — auto_direct and auto_tools — are used in place of the files pulled from /etc in the previous example.
The system decides to use NIS or files for auto_direct and auto_tools based on whether files or nis (or both) are specified in nsswitch.conf.
Even though the corresponding map names in NIS are auto_direct and auto_tools, the auto_master file uses a canonical name form, which uses underscores and not periods to separate the prefix auto from the unique suffix (direct or tools). The reason is that in some directory systems, such as NIS+, a period is a reserved character.
There is no requirement that the master map be maintained as a local file. Indeed you might find it easier if you configure your network's clients' nfsswitch.conf file to read all the maps, including the master map from NIS by setting automount: line in nsswitch.conf as:
automount: nis
This way you can exercise control over each client's namespace without having to reconfigure every client each time you want to add or delete a map from the master map. We will cover how the automounter maps are integrated into NIS later, in Section 9.3.
The default master map is not going to appear as in the examples presented so far. The default Solaris /etc/auto_master file looks something like this:
+auto_master
/net -hosts -nosuid,nobrowse
/home auto_home -nobrowse
/xfn -xfn
We will discuss the first entry, +auto_master in Section 9.3.1. The second entry, /net, will be covered in Section 9.5.2.1. The third entry, /home, will be covered in Section 9.4.1.
The last entry, /xfn, is for the X/Open Federated Naming Standard (XFN), which is a now-deprecated standard for federating directory systems. Recall from Section 2.2 that there are lots of directory services. XFN represented an attempt to allow them all to seamlessly co-exist in a global namespace. The idea was to allow users in one DNS domain to browse or access information (such as files, printers, or calendars) from another domain, even if the naming system that organized the information did not easily support cross-domain operations (as is the case with NIS). Because it appears that the world will be unifying under LDAP, and because nsswitch.conf meets most of the requirements for directory service switching, XFN has been deprecated. While the /xfn entry persists to allow you to browse any NIS or files data represented in XFN, expect XFN and /xfn to disappear from future Solaris releases.
Command-line options
The autofs automounter is started during the boot sequence from the /etc/init.d/autofs script. The automounter consists of two programs:
automount
Used to initialize the automounter's