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|System Administration Guide: Devices and File Systems Oracle Solaris 10 1/13 Information Library|
Before you can access the files on a file system, you need to mount the file system. When you mount a file system, you attach that file system to a directory (mount point) and make it available to the system. The root (/) file system is always mounted. Any other file system can be connected or disconnected from the root (/) file system.
Most file systems are automatically mounted by SMF services at system boot time. Generally, you do not need to mount or unmount file systems manually. For more information about mounting different file system types, see Mounting and Unmounting Oracle Solaris File Systems.
When you mount a file system, any files or directories in the underlying mount point directory are unavailable as long as the file system is mounted. These files are not permanently affected by the mounting process. They become available again when the file system is unmounted. However, mount directories are typically empty because you usually do not want to obscure existing files.
For step-by-step instructions on how to mount file systems, see Mounting and Unmounting Oracle Solaris File Systems.
Whenever you mount or unmount a file system, the /etc/mnttab (mount table) file is modified with the list of currently mounted file systems. You can display the contents of this file by using the cat or more commands. However, you cannot edit this file. Here is an example of an /etc/mnttab file:
$ more /etc/mnttab rpool/ROOT/zfsBE / zfs dev=3390002 0 /devices /devices devfs dev=8580000 1337114941 /dev /dev dev dev=85c0000 1337114941 ctfs /system/contract ctfs dev=8680001 1337114941 proc /proc proc dev=8600000 1337114941 mnttab /etc/mnttab mntfs dev=86c0001 1337114941 swap /system/volatile tmpfs xattr,dev=8700001 1337114941 objfs /system/object objfs dev=8740001 1337114941 sharefs /etc/dfs/sharetab sharefs dev=8780001 1337114941 /usr/lib/libc/libc_hwcap2.so.1 /lib/libc.so.1 lofs dev=3390002 13371149 fd /dev/fd fd rw,dev=8880001 1337114969 rpool/ROOT/zfsBE/var /var zfs rw,devices, setuid,nonbmand,exec, rstchown,xattr,atime,dev=3390003 1337114969 swap /tmp tmpfs xattr,dev=8700002 1337114969 rpool/VARSHARE /var/share zfs rw,devices,setuid,nonbmand,exec, rstchown,xattr,atime,dev=3390004 1337114969
Most file systems are mounted automatically by an SMF service at system boot time.
You might need to edit the /etc/vfstab file to mount legacy or remote file systems or to make changes to the ZFS swap volume. For information about changing a ZFS swap volume, see Chapter 16, Configuring Additional Swap Space (Tasks).
To add an entry for mounting a legacy or remote file system, the information you need to specify is as follows:
The device or the NFS server where the file system resides
The file system mount point
File system type
Whether you want the file system to mount automatically when the system boots (by using the mountall command)
Any mount options
The following vfstab example is from a system that has a ZFS root file system. In addition, this system is mounting a remote file system, /users/data, from the NFS server, neo.
# cat /etc/vfstab #device device mount FS fsck mount mount #to mount to fsck point type pass at boot options # fd - /dev/fd fd - no - /proc - /proc proc - no - /dev/zvol/dsk/rpool/swap - - swap - no - /devices - /devices devfs - no - sharefs - /etc/dfs/sharetabsharefs - no - ctfs - /system/contract ctfs - no - objfs - /system/object objfs - no - swap - /tmp tmpfs - yes - neo:/users/data - /data nfs - yes -
ZFS file systems are mounted automatically by the SMF service at boot time. You can mount ZFS file systems from the vfstab by using the legacy mount feature. For more information, see Oracle Solaris ZFS Administration Guide.
For descriptions of each /etc/vfstab field and information on how to edit and use the file, see vfstab(4).
NFS is a distributed file system service that can be used to share resources (files or directories) from one system, typically a server, with other systems on the network. For example, you might want to share third-party applications or source files with users on other systems.
NFS makes the actual physical location of the resource irrelevant to the user. Instead of placing copies of commonly used files on every system, NFS allows you to place one copy on one system's disk and let all other systems access it from the network. Under NFS, remote files are virtually indistinguishable from local files.
For more information, see Chapter 4, Managing Network File Systems (Overview), in System Administration Guide: Network Services.
When you share a resource, you make it available for mounting by remote systems.
You can share a resource in these ways:
Create a ZFS share by setting the ZFS property. For example:
# share -F nfs /ufsfs
For a complete description of NFS, see Chapter 4, Managing Network File Systems (Overview), in System Administration Guide: Network Services.
Oracle's implementation of the NFS version 4 distributed file access protocol is included in the Oracle Solaris release.
NFS version 4 integrates file access, file locking, and mount protocols into a single, unified protocol to ease traversal through a firewall and improve security. The Oracle Solaris implementation of NFS version 4 is fully integrated with Kerberos V5, also known as SEAM, thus providing authentication, integrity, and privacy. NFS version 4 also enables the negotiation of security flavors to be used between the client and the server. With NFS version 4, a server can offer different security flavors for different file systems.
For more information about NFS Version 4 features, see What’s New With the NFS Service in System Administration Guide: Network Services.
You can mount NFS file system resources by using a client-side service called automounting (or autofs). The autofs service enables a system to automatically mount and unmount NFS resources whenever you access them. The resource remains mounted as long as you remain in the directory and are using a file within that directory. If the resource is not accessed for a certain period of time, it is automatically unmounted.
The autofs service provides the following features:
NFS resources don't need to be mounted when the system boots, which saves booting time.
Users don't need to know the root password to mount and unmount NFS resources.
Network traffic might be reduced because NFS resources are mounted only when they are in use.
The autofs service is initialized by the automount utility, which runs automatically when a system is booted. The automountd daemon runs continuously and is responsible for the mounting and unmounting of NFS file systems on an as-needed basis. By default, the /home file system is mounted by the automount daemon.
With autofs, you can specify multiple servers to provide the same file system. This way, if one of these servers is down, autofs can try to mount the file system from another machine.
For complete information on how to set up and administer autofs, see Chapter 5, Network File System Administration (Tasks), in System Administration Guide: Network Services.