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Parts of a UFS


File Systems Although this section doesn't apply to any specific exam objective, the information is provided to help you better understand file systems in general.

UFS is the default disk-based file system used by the Solaris operating environment. It provides the following features:

  • State flags These show the state of the file system as clean, stable, active, or unknown. These flags eliminate unnecessary file system checks. If the file system is clean or stable, fsck (file system check) is not run when the system boots.

  • Extended fundamental types (EFT) These include a 32-bit user ID (UID), a group ID (GID), and device numbers.

  • Large file systems A UFS can be as large as 1 terabyte (TB) and can have regular files up to 2 gigabytes (GB). By default, the Solaris system software does not provide striping, which is required to make a logical slice large enough for a 1TB file system. However, the Solaris Volume Manager described in Chapter 10, provides this capability.

  • By default, a UFS can have regular files larger than 2GB You must explicitly use the nolargefiles mount option to enforce a 2GB maximum file size limit.

  • Logging UFS logging is the process of writing file system updates to a log before applying the updates to a UFS file system.

  • Multiterabyte file systems A multiterabyte file system enables creation of a UFS file system with up to approximately 16 terabytes of usable space, minus approximately one percent overhead. The system must be booted under a 64-bit kernel to support a multiterabyte file system. Systems booted under a 32-bit kernel are limited to a 1 TB file system.

During the installation of the Solaris software, several UFS file systems are created on the system disk. These are Sun's default file systems. Their contents are described in Table 1.6.

Table 1.6. Solaris Default File Systems


File System




Root (/) is the top of the hierarchical file tree. It holds files and directories that make up the operating system. The root directory contains the directories and files critical for system operation, such as the kernel, the device drivers, and the programs used to boot the system. It also contains the mount point directories, in which local and remote file systems can be attached to the file tree. The root (/) file system is always in slice 0.



Provides virtual memory or swap space. Swap space is used when you're running programs too large to fit in the computer's memory. The Solaris operating environment then "swaps" programs from memory to the disk and back, as needed. Although it is not technically required, it is common for the swap slice to be located in slice 1 unless /var is set up as a file system. If /var is set up, the interactive installation places /var on slice 1, and it places swap on slice 3. The /var file system is for files and directories likely to change or grow over the life of the local system. These include system logs, vi and ex backup files, printer and email spool files, backups of OS patches, and UUCP files. On a server, it's a good idea to have these files in a separate file system so that they cannot fill up the root slice.


Entire Disk

Refers to the entire disk and is defined automatically by Sun's format utility and the Solaris installation programs. The size of this slice should not be changed.



This slice is unassigned by default. In Solaris 10, if you let the Sun installation program auto layout the slices, it will place the /var directory under slice 0 with the root file system. However, if during the installation, /var is selected to have its own slice, the installation program will place /var onto slice 1 and will move swap to slice 3.



By default, slice 4 is unassigned and available for use.



This slice is unassigned by default. In Solaris 10, the /opt directory is put under slice 0 by default with the root file system. However, if during the installation, /opt is selected to have its own slice, the installation program will place /opt onto slice 5. /opt holds additional Sun software packages and optional third-party software that have been added to a system. If a slice is not allocated for this file system during installation, the /opt directory is put in slice 0, the root (/) file system.



This slice is unassigned by default. In Solaris 10, the /usr directory is put under slice 0 by default with the root file system. However, if during the installation, /usr is selected to have its own slice, the installation program will place /usr onto slice 6. /usr contains operating system commandsalso known as executablesdesigned to be run by users. /usr also holds documentation, system programs (init and syslogd, for example), library routines, and system files and directories that can be shared with other users. Files that can be used on all types of systems (such as man pages) are in /usr/share. If /usr is placed on slice 0, slice 6 becomes an unallocated slice.



Holds files created by users. On a standard system, /home is a mount point that points to /export/home and is managed by AutoFS. See Chapter 9 for more information.

Slice Numbers and Their Location on Disk

Although root may be located on slice 0, it doesn't necessarily mean that it is located first on the disk. For example, note the following partition scheme:

Part      Tag    Flag     Cylinders         Size            Blocks
  0       root    wm     258 -   759     1000.08MB    (502/0/0)  
  1        var    wm     760 -  2265        2.93GB    (1506/0/0) 
  2     backup    wm       0 - 39417       76.69GB    (39418/0/0)
  3       swap    wu       0 -   257      513.98MB    (258/0/0)  
  4 unassigned    wm       0                0         (0/0/0)    
  5 unassigned    wm    2266 -  2767     1000.08MB    (502/0/0)  
  6        usr    wm    2768 -  6783        7.81GB    (4016/0/0) 
  7       home    wm    6784 -  9293        4.88GB    (2510/0/0) 

Notice how slice 3 starts at cylinder 0 and ends at cylinder 257. This puts slice 3 first on the disk. root is located on slice 0, which starts after slice 3 at cylinder 258. When using the interactive installation program to install the operating system, the swap partition is placed at the start of the disk beginning at cylinder 0 and the root partition is placed after the swap partition. A marginal performance increase is achieved by putting swap at the starting cylinder because of the faster rotation speeds on the outside perimeter of the disk. The interactive installation program is described in Chapter 2, "Installing the Solaris 10 Operating Environment."

You need to create (or re-create) a UFS only when you do the following:

  • Add or replace disks.

  • Change the slices of an existing disk.

  • Do a full restore on a file system.

  • Change the parameters of a file system, such as block size or free space.

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