unx33.htm

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<TD>

<P>fmli</P>

<TD>

<P>AT&amp;T Form and Menu Language Interpreter</P>

<TR>

<TD>

<P>lp</P>

<TD>

<P>LP print service</P>

<TR>

<TD>

<P>manbase</P>

<TD>

<P>Online manual pages, base system</P>

<TR>

<TD>

<P>mouse</P>

<TD>

<P>Mouse driver package</P>

<TR>

<TD>

<P>oam</P>

<TD>

<P>Operations, administration, and maintenance</P>

<TR>

<TD>

<P>pci</P>

<TD>

<P>PC-interface utilities and RS-232 service</P>

<TR>

<TD>

<P>pts</P>

<TD>

<P>Pseudo-tty support</P>

<TR>

<TD>

<P>qt</P>

<TD>

<P>Cartridge tape utilities</P>

<TR>

<TD>

<P>rpc</P>

<TD>

<P>Remote procedure call utilities</P>

<TR>

<TD>

<P>termcap</P>

<TD>

<P>AT&amp;T Termcap Compatibility Package</P>

<TR>

<TD>

<P>terminf</P>

<TD>

<P>Terminal information utilities</P>

<TR>

<TD>

<P>xcp</P>

<TD>

<P>XENIX compatibility package</P>

<TR>

<TD>

<P>xl</P>

<TD>

<P>Archive XL floppy tape utilities</P></TABLE>

<P>If disk space is not critical, make the installation easy by choosing to install everything for the overall set of packages. If space is critical, you can choose not to install those items that correspond to hardware or options you do not intend to use.



<BR></P>

<P>Once you have chosen the packages you intend to install, sum their sizes as specified in the release notes for that version and you will be ready to lay out the disk slices.

<BR></P>

<H4 ALIGN="CENTER">

<CENTER><A ID="I22" NAME="I22">

<FONT SIZE=3><B>Laying Out the Disk Slices</B>

<BR></FONT></A></CENTER></H4>

<P>Rather than use an entire disk drive for one file system, which leads to inefficiencies and other problems, UNIX systems have the ability to split a single drive into sections. These sections are called slices, as each is a slice of the disk's capacity.



<BR></P>

<P>If your system is based on a PC, the master disk will first be split into partitions, using a program that emulates the MS-DOS fdisk layout. Once the UNIX partition has been allocated, this partition becomes the logical disk drive. This chapter refers 
to this partition as if it were the entire disk drive. Non&#151;PC-based systems do not have this step and allocate space on the disk drive directly.

<BR></P>

<P>Generally a disk can be split into eight subdisks or slices, each of which the operating system treats independently as a logical disk drive. This splitting of the disk is often called partitioning or labeling the disk.

<BR></P>

<P>Why split the disk? UNIX can only place one file system per logical disk. It is advantageous to split the files across multiple file systems. You can always buy multiple disk drives, one for each file system, and one for the swap space, but placing six 

or more disk drives on a system tends to up the cost a bit. Instead, this method of subdividing the disk is used.

<BR></P>

<H3 ALIGN="CENTER">

<CENTER><A ID="I23" NAME="I23">

<FONT SIZE=4><B>Why Multiple File Systems?</B>

<BR></FONT></A></CENTER></H3>

<P><B>Damage control</B>&#151;If the system were to crash due to software error, hardware failure, or power problems, some of the disk blocks might still be in the file system cache and not have been written to disk yet. This causes damage to the file 
system structure. While the methods used try to reduce this damage, and the fsck UNIX utility can repair most damage, spreading the files across multiple file systems reduces the possibility of damage, especially to critical files needed to boot the 
system. When you split the files across disk slices, these critical files end up on slices that rarely change or are mounted read-only and never change. Their chances of being damaged and preventing you from recovering the remainder of the system are 
greatly reduced.

<BR></P>

<P><B>Access control</B>&#151;Only a complete slice can be marked as read-only or read-write. If you desire to mount the shared operating system sections as read-only to prevent changes, they have to be on their own slice.

<BR></P>

<P><B>Space management</B>&#151;Files are allocated from a pool of free space on a per-file system basis. If a user allocated a large amount of space, depleting the free space, and the entire system were a single file system, there would be no free space 
left for critical system files. The entire system would freeze when it ran out of space.

<BR></P>

<P>Using separate file systems, especially for user files, allows only that single user, or group of users, to be delayed when a file system becomes full. The system will continue to operate, allowing you to handle the problem.

<BR></P>

<P><B>Performance</B>&#151;The larger the file system, within limits, the larger its tables that have to be managed. As the disk fragments and space become scarce, the further apart the fragments of a file might be placed on the disk. Using multiple 
smaller partitions reduces the absolute distance and keeps the sizes of the tables manageable. Although the UFS file system does not suffer from table size and fragmentation problems as much as System V file systems, this is still a concern.

<BR></P>

<P><B>Backups</B>&#151;Many of the backup utilities work on a complete file system basis. If the file system is very big, it could take longer than you want to allocate to back up. Multiple smaller backups are easier to handle and recover from.

<BR></P>

<HR ALIGN=CENTER>

<NOTE>

<IMG SRC="note.gif" WIDTH = 35 HEIGHT = 35><B>NOTE:</B> Just because you are doing multiple backups does not necessarily mean you need multiple tapes. UNIX can place more than one backup on a single tape, provided there is space on the tape to hold them.

<BR></NOTE>

<HR ALIGN=CENTER>

<P>The following slices are required on all UNIX installations: root and swap.

<BR></P>

<P>The recommended additional slices are these: usr, var, opt, home, and tmp.

<BR></P>

<P>As you read the sections on each slice, make a map of your disk space and allocate each slice on the map. You will use this map when you enter the disk partitioning information as you install the system.

<BR></P>

<HR ALIGN=CENTER>

<NOTE>

<IMG SRC="imp.gif" WIDTH = 68 HEIGHT = 35><B>TIP:</B> For optimum performance, it's best to start each slice on an even cylinder boundary.

<BR>

<BR>This is easy enough to do for non-scsi disks. However, many scsi disks use zone bit recording. This means there is a different number of sectors per cylinder on the inside tracks than on the outside tracks of the disk. This means that the cylinder 
boundaries are not computable, as they vary track to track.

<BR>

<BR>However, in either case, the disk is normally described to the operating system as a combination of heads, sectors, and tracks. A cylinder boundary occurs at an even combination of heads multiplied by sectors. The operating systems tables work out more 

efficiently if the partitions occur on what it thinks by your description of the disk is a cylinder boundary.

<BR></NOTE>

<HR ALIGN=CENTER>

<H5 ALIGN="CENTER">

<CENTER><A ID="I24" NAME="I24">

<FONT SIZE=3><B>The </B><B><I>root</I></B><B> Slice</B>

<BR></FONT></A></CENTER></H5>

<P>The root slice is mounted at the top of the file system hierarchy. It is mounted automatically as the system boots, and it cannot be unmounted. All other file systems are mounted below the root.

<BR></P>

<P>The root needs to be large enough to hold the following:

<BR></P>

<UL>

<LI>The boot information and the bootable UNIX kernel, and a backup copy of the kernel in case the main one gets damaged

<BR>

<BR></LI>

<LI>Any local system configuration files, which are typically in the /etc directory

<BR>

<BR></LI>

<LI>Any stand-alone programs, such as diagnostics, that might be run instead of the OS

<BR>

<BR></LI></UL>

<P>This partition typically runs on between 10 and 20 MB. It is also usually placed on the first slice of the disk, often called slice 0 or the a slice.

<BR></P>

<HR ALIGN=CENTER>

<NOTE>

<IMG SRC="imp.gif" WIDTH = 68 HEIGHT = 35><B>TIP: </B>In System V&#151;based UNIX systems the recommended size from the vendor is probably sufficient for this slice. In BSD-based UNIX systems, consider increasing the size of this slice to allow for a few 
extra kernels. BSD uses prelinked kernels instead of runtime driver loading, and you will need to keep more UNIX kernels around.

<BR></NOTE>

<HR ALIGN=CENTER>

<H5 ALIGN="CENTER">

<CENTER><A ID="I25" NAME="I25">

<FONT SIZE=3><B>The </B><B><I>swap</I></B><B> Slice</B>

<BR></FONT></A></CENTER></H5>

<P>The note in the section &quot;For What Purpose&quot; describes how UNIX uses the swap slice. The default rule is that there's twice as much swap space as there is RAM installed on the system. If you have 16 MB of ram, the swap space needs to be a 
minimum of 32 MB. If you have 256 MB of RAM, the minimum swap is 512 MB.

<BR></P>

<P>This is just a starting point. If the users of this system run big applications that use large amounts of data, such as desktop publishing or CAD, this might not be enough swap. If you are unsure as to the swap needs of your users, start with the rule 
of twice RAM. Monitor the amount of swap space used via the pstat or swap commands. If you did not allocate enough, most UNIX systems support adding additional swap at runtime via the swapon or swap commands.

<BR></P>

<H5 ALIGN="CENTER">

<CENTER><A ID="I26" NAME="I26">

<FONT SIZE=3><B>The </B><B><I>usr</I></B><B> Slice</B>

<BR></FONT></A></CENTER></H5>

<P>The usr slice holds the remainder of the UNIX operating system and utilities. It needs to be large enough to hold all the packages you chose to install when you made the list earlier.

<BR></P>

<P>If you intend to install local applications or third-party applications in this slice, it needs to be large enough to hold them as well. However, it is generally better, for ease of performing upgrades, if the usr slice contains the operating system and 

only symbolic links, if necessary, to the applications.

<BR></P>

<P>This file system is often mounted read-only to prevent accidental changes.

<BR></P>

<H5 ALIGN="CENTER">

<CENTER><A ID="I27" NAME="I27">

<FONT SIZE=3><B>The </B><B><I>var</I></B><B> Slice</B>

<BR></FONT></A></CENTER></H5>

<P>The var slice holds the spool directories used to queue printer files and electronic mail, as well as log files unique to this system. It also holds the /var/tmp directory, which is used for larger temporary files. It is the read-write counterpart to 
the usr slice. Every system, even a diskless client, needs its own var file system. It cannot be shared with other systems.

<BR></P>

<HR ALIGN=CENTER>

<NOTE>

<IMG SRC="note.gif" WIDTH = 35 HEIGHT = 35><B>NOTE:</B> Although the var file system cannot be shared, subdirectories under it can (for example, /var/mail).

<BR>

<BR>These would be mounted on top of the var file system after it is already mounted.

<BR></NOTE>

<HR ALIGN=CENTER>

<P>If you do not print very large files, accept the size the release notes suggest for this slice. If you do print a large number of files or large files, or if your site will be performing a large volume of UUCP traffic, consider increasing the size of 
this slice to accommodate your needs.

<BR></P>

<HR ALIGN=CENTER>

<NOTE>

<IMG SRC="imp.gif" WIDTH = 68 HEIGHT = 35><B>TIP: </B>For print files, a good starting point is adding 10 times the size of the largest print file to the size recommended. Add more if there are a large number of users or multiple printers attached to this 

system.

<BR>

<BR>For UUCP files, have enough space to hold at least a day's worth of traffic for every site.

<BR></NOTE>

<HR ALIGN=CENTER>

<H5 ALIGN="CENTER">

<CENTER><A ID="I28" NAME="I28">

<FONT SIZE=3><B>The </B><B><I>opt</I></B><B> Slice</B>

<BR></FONT></A></CENTER></H5>

<P>In the newer UNIX systems based on System V Release 4 (Solaris 2.x, UnixWare, and so on), many sections of the operating system are considered optional and are no longer installed on the /usr file system. They are now installed into the /opt file 
system. In addition, they place add-on packages in this file system.

<BR></P>

<P>To size this partition, take the suggested size from the release notes, and add to that the size of any add-on packages you plan to install.

<BR></P>

<HR ALIGN=CENTER>

<NOTE>

<IMG SRC="imp.gif" WIDTH = 68 HEIGHT = 35><B>TIP: </B>Don't worry too much about getting it right. If you need to install an add-on package later and there is not enough room left in opt, install the package elsewhere and create a symbolic link from where 

you did install it back into /opt.

<BR></NOTE>

<HR ALIGN=CENTER>

<H5 ALIGN="CENTER">