Overview of Mounting and Unmounting File Systems

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.

The Mounted File System Table

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

The Virtual File System Table

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 11.1 Administration: ZFS File Systems.

For descriptions of each /etc/vfstab field and information on how to edit and use the file, see vfstab(4).

The NFS Environment

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 Oracle Solaris Administration: Network Services.

A system becomes an NFS server if it has resources to share on the network. A server keeps a list of currently shared resources and their access restrictions (such as read/write or read-only access).

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 share.nfs property. For example:

  # zfs set share.nfs=on tank/home

• Create a legacy share by using the share command.

  # share -F nfs /ufsfs

For a complete description of NFS, see Chapter 4, Managing Network File Systems (Overview), in Oracle Solaris Administration: Network Services.

NFS Version 4

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 Oracle Solaris Administration: Network Services.

Automounting (autofs)

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 2, Network File System Administration (Tasks), in Managing Network File Systems in Oracle Solaris 11.1.

The Oracle Solaris SMB Service

The Oracle Solaris OS provides a Server Message Block (SMB) protocol server and client implementation that includes support for numerous SMB dialects including NT LM 0.12 and Common Internet File System (CIFS). The terms CIFS and SMB can be considered interchangeable.

The Solaris SMB server allows a native Oracle Solaris system to serve files as SMB shares to SMB enabled clients that mount the file system shares. A Windows, Mac OS, or Solaris client can interoperate with the Solaris SMB server as it would with a Windows server. A Solaris SMB server can operate in either workgroup mode or in domain mode. In workgroup mode, the Solaris SMB server is responsible for authenticating users locally when access is requested to shared resources. This authentication process is referred to as local login. In domain mode, the Solaris SMB server uses pass-through authentication, in which user authentication is delegated to a domain controller.

For more information, see Managing SMB File Sharing and Windows Interoperability in Oracle Solaris 11.1.