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(itstool) path: sect1/para

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Temporary files which are usually preserved across a system reboot, unless <filename>/var</filename> is a memory-based file system.
<filename>/var/yp/</filename>
NIS maps.
Disk Organization
The smallest unit of organization that FreeBSD uses to find files is the filename. Filenames are case-sensitive, which means that <filename>readme.txt</filename> and <filename>README.TXT</filename> are two separate files. FreeBSD does not use the extension of a file to determine whether the file is a program, document, or some other form of data.
Files are stored in directories. A directory may contain no files, or it may contain many hundreds of files. A directory can also contain other directories, allowing a hierarchy of directories within one another in order to organize data.
Files and directories are referenced by giving the file or directory name, followed by a forward slash, <literal>/</literal>, followed by any other directory names that are necessary. For example, if the directory <filename>foo</filename> contains a directory <filename>bar</filename> which contains the file <filename>readme.txt</filename>, the full name, or <firstterm>path</firstterm>, to the file is <filename>foo/bar/readme.txt</filename>. Note that this is different from <trademark class="registered">Windows</trademark> which uses <literal>\</literal> to separate file and directory names. FreeBSD does not use drive letters, or other drive names in the path. For example, one would not type <filename>c:\foo\bar\readme.txt</filename> on FreeBSD.
Directories and files are stored in a file system. Each file system contains exactly one directory at the very top level, called the <firstterm>root directory</firstterm> for that file system. This root directory can contain other directories. One file system is designated the <firstterm>root file system</firstterm> or <literal>/</literal>. Every other file system is <firstterm>mounted</firstterm> under the root file system. No matter how many disks are on the FreeBSD system, every directory appears to be part of the same disk.
Consider three file systems, called <literal>A</literal>, <literal>B</literal>, and <literal>C</literal>. Each file system has one root directory, which contains two other directories, called <literal>A1</literal>, <literal>A2</literal> (and likewise <literal>B1</literal>, <literal>B2</literal> and <literal>C1</literal>, <literal>C2</literal>).
Call <literal>A</literal> the root file system. If <citerefentry><refentrytitle>ls</refentrytitle><manvolnum>1</manvolnum></citerefentry> is used to view the contents of this directory, it will show two subdirectories, <literal>A1</literal> and <literal>A2</literal>. The directory tree looks like this:
_ external ref='basics/example-dir1' md5='__failed__'
/
|
+--- A1
|
`--- A2
A file system must be mounted on to a directory in another file system. When mounting file system <literal>B</literal> on to the directory <literal>A1</literal>, the root directory of <literal>B</literal> replaces <literal>A1</literal>, and the directories in <literal>B</literal> appear accordingly:
_ external ref='basics/example-dir2' md5='__failed__'
/
|
+--- A1
| |
| +--- B1
| |
| `--- B2
|
`--- A2
Any files that are in the <literal>B1</literal> or <literal>B2</literal> directories can be reached with the path <filename>/A1/B1</filename> or <filename>/A1/B2</filename> as necessary. Any files that were in <filename>/A1</filename> have been temporarily hidden. They will reappear if <literal>B</literal> is <firstterm>unmounted</firstterm> from <literal>A</literal>.
If <literal>B</literal> had been mounted on <literal>A2</literal> then the diagram would look like this:
_ external ref='basics/example-dir3' md5='__failed__'
/
|
+--- A1
|
`--- A2
|
+--- B1
|
`--- B2
and the paths would be <filename>/A2/B1</filename> and <filename>/A2/B2</filename> respectively.
File systems can be mounted on top of one another. Continuing the last example, the <literal>C</literal> file system could be mounted on top of the <literal>B1</literal> directory in the <literal>B</literal> file system, leading to this arrangement:
_ external ref='basics/example-dir4' md5='__failed__'
/
|
+--- A1
|
`--- A2
|
+--- B1
| |
| +--- C1
| |
| `--- C2
|
`--- B2
Or <literal>C</literal> could be mounted directly on to the <literal>A</literal> file system, under the <literal>A1</literal> directory:
_ external ref='basics/example-dir5' md5='__failed__'
/
|
+--- A1
| |
| +--- C1
| |
| `--- C2
|
`--- A2
|
+--- B1
|
`--- B2
It is entirely possible to have one large root file system, and not need to create any others. There are some drawbacks to this approach, and one advantage.
Benefits of Multiple File Systems
Different file systems can have different <firstterm>mount options</firstterm>. For example, the root file system can be mounted read-only, making it impossible for users to inadvertently delete or edit a critical file. Separating user-writable file systems, such as <filename>/home</filename>, from other file systems allows them to be mounted <firstterm>nosuid</firstterm>. This option prevents the <firstterm>suid</firstterm>/<firstterm>guid</firstterm> bits on executables stored on the file system from taking effect, possibly improving security.
FreeBSD automatically optimizes the layout of files on a file system, depending on how the file system is being used. So a file system that contains many small files that are written frequently will have a different optimization to one that contains fewer, larger files. By having one big file system this optimization breaks down.
FreeBSD's file systems are robust if power is lost. However, a power loss at a critical point could still damage the structure of the file system. By splitting data over multiple file systems it is more likely that the system will still come up, making it easier to restore from backup as necessary.

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Source string comment

(itstool) path: sect1/para

Flags
read-only
Source string location
book.translate.xml:7682
String age
a year ago
Source string age
a year ago
Translation file
books/handbook.pot, string 1240