Now that we know how to move around the file system, it’s time for a guided tour of our Linux system. Before we start however, we’re going to learn some more commands that will be useful along the way:
既然我們已經知道了如何在檔案系統中跳轉，是時候開始 Linux 作業系統之旅了。然而在開始之前，我們先學習一些對研究 Linux 系統有幫助的命令。
ls – List directory contents
file – Determine file type
less – View file contents
ls — 列出目錄內容
file — 確定檔案型別
less — 瀏覽檔案內容
The ls command is probably the most used command, and for good reason. With it, we can see directory contents and determine a variety of important file and directory attributes. As we have seen, we can simply type ls to see a list of files and subdirectories contained in the current working directory:
ls 可能是使用者最常使用的命令了，這自有它的道理。透過它，我們可以知道目錄的內容，以及各種各樣重要檔案和目錄的 屬性。正如我們已經見到的，只要簡單地輸入 ls 就能看到在當前目錄下所有檔案和子目錄的列表。
[me@linuxbox ~]$ ls
Desktop Documents Music Pictures Publica Templates Videos
Besides the current working directory, we can specify the directory to list, like so:
除了當前工作目錄以外，也可以指定別的目錄，就像這樣：
me@linuxbox ~]$ ls /usr
bin games kerberos libexec sbin src
etc include lib local share tmp
Or even specify multiple directories. In this example we will list both the user’s home directory (symbolized by the “~” character) and the /usr directory:
甚至可以列出多個指定目錄的內容。在這個例子中，將會列出使用者家目錄（用字元“~”代表）和/usr 目錄的內容：
[me@linuxbox ~]$ ls ~ /usr
/home/me:
Desktop Documents Music Pictures Public Templates Videos
/usr:
bin games kerberos libexec sbin src
etc include lib local share tmp
We can also change the format of the output to reveal more detail:
我們也可以改變輸出格式，來得到更多的細節：
[me@linuxbox ~]$ ls -l
total 56
drwxrwxr-x 2 me me 4096 2007-10-26 17:20 Desktop
drwxrwxr-x 2 me me 4096 2007-10-26 17:20 Documents
drwxrwxr-x 2 me me 4096 2007-10-26 17:20 Music
drwxrwxr-x 2 me me 4096 2007-10-26 17:20 Pictures
drwxrwxr-x 2 me me 4096 2007-10-26 17:20 Public
drwxrwxr-x 2 me me 4096 2007-10-26 17:20 Templates
drwxrwxr-x 2 me me 4096 2007-10-26 17:20 Videos
By adding “-l” to the command, we changed the output to the long format.
使用 ls 命令的“-l”選項，則結果以長模式輸出。
This brings us to a very important point about how most commands work. Commands are often followed by one or more options that modify their behavior, and further, by one or more arguments, the items upon which the command acts. So most commands look kind of like this:
我們將學習一個非常重要的知識點，即大多數命令是如何工作的。命令名經常會帶有一個或多個用來更正命令列為的選項， 更進一步，選項後面會帶有一個或多個引數，這些引數是命令作用的物件。所以大多數命令看起來像這樣：
command -options arguments
Most commands use options consisting of a single character preceded by a dash, for example, “-l”, but many commands, including those from the GNU Project, also support long options, consisting of a word preceded by two dashes. Also, many commands allow multiple short options to be strung together. In this example, the ls command is given two options, the “l” option to produce long format output, and the “t” option to sort the result by the file’s modification time.
大多數命令使用的選項，是由一箇中劃線加上一個字元組成，例如，“-l”，但是許多命令，包括來自於 GNU 專案的命令，也支援長選項，長選項由兩個中劃線加上一個字組成。當然， 許多命令也允許把多個短選項串在一起使用。下面這個例子，ls 命令有兩個選項， “l” 選項產生長格式輸出，“t”選項按檔案修改時間的先後來排序。
[me@linuxbox ~]$ ls -lt
We’ll add the long option “–reverse” to reverse the order of the sort:
加上長選項 “–reverse”，則結果會以相反的順序輸出：
[me@linuxbox ~]$ ls -lt --reverse
The ls command has a large number of possible options. The most common are listed in the Table 4-1.
ls 命令有大量的選項。表4-1列出了最常使用的選項。
| Option | Long Option | Description |
|---|---|---|
| -a | --all | List all files, even those with names that begin with a period, which are normally not listed(i.e.,hidden). |
| -d | --directory | Ordinaryly,if a directory is specified, ls will list the contents of the directory, not the directory itself. Use this option in conjunction with the -l option to see details about the directory rather than its contents. |
| -F | --classify | This option will append an indicator character to the end of each listed name. For example, a '/' if the name is a directory. |
| -h | --human-readable | In long format listings, display file sizes in human readable format rather than in bytes. |
| -l | Display results in long format. | |
| -r | --reverse | Display the results in reverse order. Normally, ls display its results in ascending alphabetical order. |
| -S | Sort results by file size. | |
| -t | Sort by modification time. |
| 選項 | 長選項 | 描述 |
|---|---|---|
| -a | --all | 列出所有檔案，甚至包括檔名以圓點開頭的預設會被隱藏的隱藏檔案。 |
| -d | --directory | 通常，如果指定了目錄名，ls 命令會列出這個目錄中的內容，而不是目錄本身。 把這個選項與 -l 選項結合使用，可以看到所指定目錄的詳細資訊，而不是目錄中的內容。 |
| -F | --classify | 這個選項會在每個所列出的名字後面加上一個指示符。例如，如果名字是 目錄名，則會加上一個'/'字元。 |
| -h | --human-readable | 當以長格式列出時，以人們可讀的格式，而不是以位元組數來顯示檔案的大小。 |
| -l | 以長格式顯示結果。 | |
| -r | --reverse | 以相反的順序來顯示結果。通常，ls 命令的輸出結果按照字母升序排列。 |
| -S | 命令輸出結果按照檔案大小來排序。 | |
| -t | 按照修改時間來排序。 |
As we saw before, the “-l” option causes ls to display its results in long format. This format contains a great deal of useful information. Here is the Examples directory from an Ubuntu system:
正如我們先前知道的，“-l”選項導致 ls 的輸出結果以長格式輸出。這種格式包含大量的有用資訊。下面的例子目錄來自 於 Ubuntu 系統：
-rw-r--r-- 1 root root 3576296 2007-04-03 11:05 Experience ubuntu.ogg
-rw-r--r-- 1 root root 1186219 2007-04-03 11:05 kubuntu-leaflet.png
-rw-r--r-- 1 root root 47584 2007-04-03 11:05 logo-Edubuntu.png
-rw-r--r-- 1 root root 44355 2007-04-03 11:05 logo-Kubuntu.png
-rw-r--r-- 1 root root 34391 2007-04-03 11:05 logo-Ubuntu.png
-rw-r--r-- 1 root root 32059 2007-04-03 11:05 oo-cd-cover.odf
-rw-r--r-- 1 root root 159744 2007-04-03 11:05 oo-derivatives.doc
-rw-r--r-- 1 root root 27837 2007-04-03 11:05 oo-maxwell.odt
-rw-r--r-- 1 root root 98816 2007-04-03 11:05 oo-trig.xls
-rw-r--r-- 1 root root 453764 2007-04-03 11:05 oo-welcome.odt
-rw-r--r-- 1 root root 358374 2007-04-03 11:05 ubuntu Sax.ogg
Let's look at the different fields from one of the files and examine their meanings:
選一個檔案，來看一下各個輸出欄位的含義：
| Field | Meaning |
|---|---|
| -rw-r--r-- | Access rights to the file. The first character indicates the type of file. Among the different types, a leading dash means a regular file, while a “d” indicates a directory. The next three characters are the access rights for the file's owner, the next three are for members of the file's group, and the final three are for everyone else. The full meaning of this is discussed in Chapter 10 – Permissions. |
| 1 | File's number of hard links. See the discussion of links later in this chapter. |
| root | The user name of the file's owner. |
| root | The name of the group which owns the file. |
| 32059 | Size of the file in bytes. |
| 2007-04-03 11:05 | Date and time of the file's last modification. |
| oo-cd-cover.odf | Name of the file. |
| 欄位 | 含義 |
|---|---|
| -rw-r--r-- | 對於檔案的訪問許可權。第一個字元指明檔案型別。在不同型別之間， 開頭的“－”說明是一個普通檔案，“d”表明是一個目錄。其後三個字元是檔案所有者的 訪問許可權，再其後的三個字元是檔案所屬組中成員的訪問許可權，最後三個字元是其他所 有人的訪問許可權。這個欄位的完整含義將在第十章討論。 |
| 1 | 檔案的硬連結數目。參考隨後討論的關於連結的內容。 |
| root | 檔案所有者的使用者名稱。 |
| root | 檔案所屬使用者組的名字。 |
| 32059 | 以位元組數表示的檔案大小。 |
| 2007-04-03 11:05 | 上次修改檔案的時間和日期。 |
| oo-cd-cover.odf | 檔名。 |
As we explore the system it will be useful to know what files contain. To do this we will use the file command to determine a file’s type. As we discussed earlier, filenames in Linux are not required to reflect a file’s contents. While a filename like “picture.jpg” would normally be expected to contain a JPEG compressed image, it is not required to in Linux. We can invoke the file command this way:
隨著探究作業系統的進行，知道檔案包含的內容是很有用的。我們將用 file 命令來確定檔案的型別。我們之前討論過， 在 Linux 系統中，並不要求檔名來反映檔案的內容。然而，一個類似 “picture.jpg” 的檔名，我們會期望它包含 JPEG 壓縮影象，但 Linux 卻不這樣要求它。可以這樣呼叫 file 命令：
file filename
When invoked, the file command will print a brief description of the file’s contents. For example:
當呼叫 file 命令後，file 命令會打印出檔案內容的簡單描述。例如：
[me@linuxbox ~]$ file picture.jpg
picture.jpg: JPEG image data, JFIF standard 1.01
There are many kinds of files. In fact, one of the common ideas in Unix-like operating systems such as Linux is that “everything is a file.” As we proceed with our lessons, we will see just how true that statement is.
有許多種型別的檔案。事實上，在類別 Unix 作業系統中比如說 Linux 中，有個普遍的觀念就是“一切皆檔案”。 隨著課程的進行，我們將會明白這句話是多麼的正確。
While many of the files on your system are familiar, for example MP3 and JPEG, there are many kinds that are a little less obvious and a few that are quite strange.
雖然系統中許多檔案格式是熟悉的，例如 MP3和 JPEG 檔案，但也有一些檔案格式不太常見，極少數檔案相當陌生。
The less command is a program to view text files. Throughout our Linux system, there are many files that contain human-readable text. The less program provides a convenient way to examine them.
less 命令是一個用來瀏覽文字檔案的程式。縱觀 Linux 系統，有許多人類可讀的文字檔案。less 程式為我們檢查文字檔案 提供了方便。
What Is “Text”
什麼是“文字”
There are many ways to represent information on a computer. All methods involve defining a relationship between the information and some numbers that will be used to represent it. Computers, after all, only understand numbers and all data is converted to numeric representation.
在計算機中，有許多方法可以表達資訊。所有的方法都涉及到，在資訊與一些數字之間確立一種關係，而這些數字可以 用來代表資訊。畢竟，計算機只能理解數字，這樣所有的資料都被轉換成數值來表示。
Some of these representation systems are very complex (such as compressed video files), while others are rather simple. One of the earliest and simplest is called ASCII text. ASCII (pronounced “As-Key”) is short for American Standard Code for Information Interchange. This is a simple encoding scheme that was first used on Teletype machines to map keyboard characters to numbers.
有些數值表達法非常複雜（例如壓縮的視訊檔案），而其它的就相當簡單。最早也是最簡單的一種表達法，叫做 ASCII 文字。ASCII（發音是”As-Key”）是美國資訊交換標準碼的簡稱。這是一個簡單的編碼方法，它首先 被用在電傳打字機上，用來實現鍵盤字元到數字的對映。
Text is a simple one-to-one mapping of characters to numbers. It is very compact. Fifty characters of text translates to fifty bytes of data. It is important to understand that text only contains a simple mapping of characters to numbers. It is not the same as a word processor document such as one created by Microsoft Word or OpenOffice.org Writer. Those files, in contrast to simple ASCII text, contain many non-text elements that are used to describe its structure and formatting. Plain ASCII text files contain only the characters themselves and a few rudimentary control codes like tabs, carriage returns and line feeds. Throughout a Linux system, many files are stored in text format and there are many Linux tools that work with text files. Even Windows recognizes the importance of this format. The well-known NOTEPAD.EXE program is an editor for plain ASCII text files.
文字是簡單的字元與數字之間的一對一對映。它非常緊湊。五十個字元的文字翻譯成五十個位元組的資料。文字只是包含 簡單的字元到數字的對映，理解這點很重要。它和一些文書處理器文件不一樣，比如說由微軟或 OpenOffice.org 文件 編輯器建立的檔案。這些檔案，和簡單的 ASCII 檔案形成鮮明對比，它們包含許多非文字元素，來描述它的結構和格式。 純 ASCII 檔案只包含字元本身，和一些基本的控制符，像製表符、回車符及換行符。縱觀 Linux 系統，許多檔案以文字格式儲存，也有許多 Linux 工具來處理文字檔案。甚至 Windows 也承認這種檔案格式的重要性。著名的 NOTEPAD.EXE 程式就是一個純 ASCII 文字檔案編輯器。
Why would we want to examine text files? Because many of the files that contain system settings (called configuration files) are stored in this format, and being able to read them gives us insight about how the system works. In addition, many of the actual programs that the system uses (called scripts) are stored in this format. In later chapters, we will learn how to edit text files in order to modify systems settings and write our own scripts, but for now we will just look at their contents.
為什麼我們要檢視文字檔案呢？ 因為許多包含系統設定的檔案（叫做配置檔案），是以文字格式儲存的，閱讀它們 可以更深入的瞭解系統是如何工作的。另外，許多系統所用到的實際程式（叫做指令碼）也是以這種格式儲存的。 在隨後的章節裡，我們將要學習怎樣編輯文字檔案以修改系統設定，還要學習編寫自己的指令碼檔案，但現在我們只是看看它們的內容而已。
The less command is used like this:
less 命令是這樣使用的：
less filename
Once started, the less program allows you to scroll forward and backward through a text file. For example, to examine the file that defines all the system’s user accounts, enter the following command:
一旦執行起來，less 程式允許你前後滾動檔案。例如，要檢視一個定義了系統中全部使用者身份的檔案，輸入以下命令：
[me@linuxbox ~]$ less /etc/passwd
Once the less program starts, we may view the contents of the file. If the file is longer than one page, we can scroll up and down. To exit less, press the “q” key. The table below lists the most common keyboard commands used by less.
一旦 less 程式執行起來，我們就能瀏覽檔案內容了。如果檔案內容多於一頁，那麼我們可以上下滾動檔案。按下“q”鍵， 退出 less 程式。
下表列出了 less 程式最常使用的鍵盤命令。
| Command | Action |
|---|---|
| Page UP or b | Scroll back one page |
| Page Down or space | Scroll forward one page |
| UP Arrow | Scroll Up one line |
| Down Arrow | Scrow Down one line |
| G | Move to the end of the text file |
| 1G or g | Move to the beginning of the text file |
| /charaters | Search forward for the next occurrence of characters |
| n | Search forward for the next occurrence of the previous search |
| h | Display help screen |
| q | Quit less |
| 命令 | 行為 |
|---|---|
| Page UP or b | 向上翻滾一頁 |
| Page Down or space | 向下翻滾一頁 |
| UP Arrow | 向上翻滾一行 |
| Down Arrow | 向下翻滾一行 |
| G | 移動到最後一行 |
| 1G or g | 移動到開頭一行 |
| /charaters | 向前查詢指定的字串 |
| n | 向前查詢下一個出現的字串，這個字串是之前所指定查詢的 |
| h | 顯示幫助螢幕 |
| q | 退出 less 程式 |
The less program was designed as an improved replacement of an earlier Unix program called more. The name “less” is a play on the phrase “less is more”—a motto of modernist architects and designers.
less 程式是早期 Unix 程式 more 的改進版。“less” 這個名字，對習語 “less is more” 開了個玩笑， 這個習語是現代主義建築師和設計者的座右銘。
less falls into the class of programs called “pagers,” programs that allow the easy viewing of long text documents in a page by page manner. Whereas the more program could only page forward, the less program allows paging both forward and backward and has many other features as well.
less 屬於”頁面排程器”類別程式，這些程式允許以逐頁方式輕鬆瀏覽長文字文件。 more 程式只能向前翻頁，而 less 程式允許前後翻頁，此外還有很多其它的特性。
The file system layout on your Linux system is much like that found on other Unix-like systems. The design is actually specified in a published standard called the Linux Filesystem Hierarchy Standard. Not all Linux distributions conform to the standard exactly but most come pretty close.
Linux 系統中，檔案系統佈局與類別 Unix 系統的檔案佈局很相似。實際上，一個已經發布的標準， 叫做 Linux 檔案系統層次標準，詳細說明了這種設計模式。不是所有Linux發行版都根據這個標準，但 大多數都是。
Next, we are going to wander around the file system ourselves to see what makes our Linux system tick. This will give you a chance to practice your navigation skills. One of the things we will discover is that many of the interesting files are in plain human- readable text. As we go about our tour, try the following:
下一步，我們將在檔案系統中漫遊，來了解 Linux 系統的工作原理。這會給你一個溫習跳轉命令的機會。 我們會發現很多有趣的檔案都是純人類可讀文字。下面旅行開始，做做以下練習：
If it looks like it might be text, try viewing it with less
Remember the copy and paste trick! If you are using a mouse, you can double click on a filename to copy it and middle click to paste it into commands.
記得複製和貼上技巧！如果你正在使用滑鼠，雙擊檔名，來複制它，然後按下滑鼠中鍵，貼上檔名到命令列中。
As we wander around, don’t be afraid to look at stuff. Regular users are largely prohibited from messing things up. That’s the system administrators job! If a command complains about something, just move on to something else. Spend some time looking around. The system is ours to explore. Remember, in Linux, there are no secrets! Table 4-4 lists just a few of the directories we can explore. Feel free to try more!
在系統中漫遊時，不要害怕四處看看。普通使用者是很難把東西弄亂的。那是系統管理員的工作！ 如果一個命令抱怨一些事情，不要管它，嘗試一下別的東西。花一些時間四處看看。 系統是我們自己的，盡情地探究吧。記住在 Linux 中，沒有祕密存在！ 表4-4僅僅列出了一些我們可以瀏覽的目錄。隨意嘗試更多！
| Drectory | Comments |
|---|---|
| / | The root directory.Where everything begins. |
| /bin | Contains binaries (programs) that must be present for the system to boot and run. |
| /boot | Contains the linux kernel, intial RAM disk image (for
drivers needed at boot time), and the boot loader.
Interesting files:
|
| /dev | This is a special directory which contains device nodes. "Everything is a file" also applies to devices. Here is where the kernel maintains a list of all the devices it understands. |
| /etc | The /etc directory contains all of the system-wide
configuration files. It also contains a collection of shell scripts which start
each of the system services at boot time. Everything in this directory should
be readable text.
Interesting files:While everything in /etc is interesting, here are some of my all-time favorites:
|
| /home | In normal configurations, each user is given a directory in /home. Ordinary users can only write files in their home directories. This limitation protects the system from errant user activity. |
| /lib | Contains shared library files used by the core system programs. These are similar to DLLs in Windows. |
| /lost+found | Each formatted partition or device using a Linux file system, such as ext3, will have this directory. It is used in the case of a partial recovery from a file system corruption event. Unless something really bad has happened to your system, this directory will remain empty. |
| /media | On modern Linux systems the /media directory will contain the mount points for removable media such USB drives, CD-ROMs, etc. that are mounted automatically at insertion. |
| /mnt | On older Linux systems, the /mnt directory contains mount points for removable devices that have been mounted manually. |
| /opt | The /opt directory is used to install “optional” software. This is mainly used to hold commercial software products that may be installed on your system. |
| /proc | The /proc directory is special. It's not a real file system in the sense of files stored on your hard drive. Rather, it is a virtual file system maintained by the Linux kernel. The “files” it contains are peepholes into the kernel itself. The files are readable and will give you a picture of how the kernel sees your computer. |
| /root | This is the home directory for the root account. |
| /sbin | This directory contains “system” binaries. These are programs that perform vital system tasks that are generally reserved for the superuser. |
| /tmp | The /tmp directory is intended for storage of temporary, transient files created by various programs. Some configurations cause this directory to be emptied each time the system is rebooted. |
| /usr | The /usr directory tree is likely the largest one on a Linux system. It contains all the programs and support files used by regular users. |
| /usr/bin | /usr/bin contains the executable programs installed by your Linux distribution. It is not uncommon for this directory to hold thousands of programs. |
| /usr/lib | The shared libraries for the programs in /usr/bin. |
| /usr/local | The /usr/local tree is where programs that are not included with your distribution but are intended for system- wide use are installed. Programs compiled from source code are normally installed in /usr/local/bin. On a newly installed Linux system, this tree exists, but it will be empty until the system administrator puts something in it. |
| /usr/sbin | Contains more system administration programs. |
| /usr/share | /usr/share contains all the shared data used by programs in /usr/bin. This includes things like default configuration files, icons, screen backgrounds, sound files, etc. |
| /usr/share/doc | Most packages installed on the system will include some kind of documentation. In /usr/share/doc, we will find documentation files organized by package. |
| /var | With the exception of /tmp and /home, the directories we have looked at so far remain relatively static, that is, their contents don't change. The /var directory tree is where data that is likely to change is stored. Various databases, spool files, user mail, etc. are located here. |
| /var/log | /var/log contains log files, records of various system activity. These are very important and should be monitored from time to time. The most useful one is /var/log/messages. Note that for security reasons on some systems, you must be the superuser to view log files. |
| 目錄 | 評論 |
|---|---|
| / | 根目錄，萬物起源。 |
| /bin | 包含系統啟動和執行所必須的二進位制程式。 |
| /boot | 包含 Linux 核心、初始 RAM 磁碟映像（用於啟動時所需的驅動）和 啟動載入程式。 有趣的檔案：
|
| /dev | 這是一個包含裝置結點的特殊目錄。“一切都是檔案”，也適用於裝置。 在這個目錄裡，核心維護著所有裝置的列表。 |
| /etc | 這個目錄包含所有系統層面的配置檔案。它也包含一系列的 shell 指令碼， 在系統啟動時，這些指令碼會開啟每個系統服務。這個目錄中的任何檔案應該是可讀的文字檔案。 有趣的檔案：雖然/etc 目錄中的任何檔案都有趣，但這裡只列出了一些我一直喜歡的檔案：
|
| /home | 在通常的配置環境下，系統會在/home 下，給每個使用者分配一個目錄。普通使用者只能 在自己的目錄下寫檔案。這個限制保護系統免受錯誤的使用者活動破壞。 |
| /lib | 包含核心系統程式所使用的共享函式庫檔案。這些檔案與 Windows 中的動態連結函式庫相似。 |
| /lost+found | 每個使用 Linux 檔案系統的格式化分割槽或裝置，例如 ext3檔案系統， 都會有這個目錄。當部分恢復一個損壞的檔案系統時，會用到這個目錄。這個目錄應該是空的，除非檔案系統 真正的損壞了。 |
| /media | 在現在的 Linux 系統中，/media 目錄會包含可移動介質的掛載點， 例如 USB 驅動器，CD-ROMs 等等。這些介質連線到計算機之後，會自動地掛載到這個目錄結點下。 |
| /mnt | 在早些的 Linux 系統中，/mnt 目錄包含可移動介質的掛載點。 |
| /opt | 這個/opt 目錄被用來安裝“可選的”軟體。這個主要用來儲存可能 安裝在系統中的商業軟體產品。 |
| /proc | 這個/proc 目錄很特殊。從儲存在硬碟上的檔案的意義上說，它不是真正的檔案系統。 相反，它是一個由 Linux 核心維護的虛擬檔案系統。它所包含的檔案是核心的窺視孔。這些檔案是可讀的， 它們會告訴你核心是怎樣監管計算機的。 |
| /root | root 帳戶的家目錄。 |
| /sbin | 這個目錄包含“系統”二進位制檔案。它們是完成重大系統任務的程式，通常為超級使用者保留。 |
| /tmp | 這個/tmp 目錄，是用來儲存由各種程式建立的臨時檔案的地方。一些配置導致系統每次 重新啟動時，都會清空這個目錄。 |
| /usr | 在 Linux 系統中，/usr 目錄可能是最大的一個。它包含普通使用者所需要的所有程式和檔案。 |
| /usr/bin | /usr/bin 目錄包含系統安裝的可執行程式。通常，這個目錄會包含許多程式。 |
| /usr/lib | 包含由/usr/bin 目錄中的程式所用的共享函式庫。 |
| /usr/local | 這個/usr/local 目錄，是非系統發行版自帶程式的安裝目錄。 通常，由原始碼編譯的程式會安裝在/usr/local/bin 目錄下。新安裝的 Linux 系統中會存在這個目錄， 並且在管理員安裝程式之前，這個目錄是空的。 |
| /usr/sbin | 包含許多系統管理程式。 |
| /usr/share | /usr/share 目錄包含許多由/usr/bin 目錄中的程式使用的共享資料。 其中包括像預設的配置檔案、圖示、桌面背景、音訊檔案等等。 |
| /usr/share/doc | 大多數安裝在系統中的軟體包會包含一些文件。在/usr/share/doc 目錄下， 我們可以找到按照軟體包分類的文件。 |
| /var | 除了/tmp 和/home 目錄之外，相對來說，目前我們看到的目錄是靜態的，這是說， 它們的內容不會改變。/var 目錄存放的是動態檔案。各種資料庫，假離線檔案， 使用者郵件等等，都位於在這裡。 |
| /var/log | 這個/var/log 目錄包含日誌檔案、各種系統活動的記錄。這些檔案非常重要，並且 應該時時監測它們。其中最重要的一個檔案是/var/log/messages。注意，為了系統安全，在一些系統中， 你必須是超級使用者才能檢視這些日誌檔案。 |
As we look around, we are likely to see a directory listing with an entry like this:
在我們到處檢視時，我們可能會看到一個目錄，列出像這樣的一條資訊：
lrwxrwxrwx 1 root root 11 2007-08-11 07:34 libc.so.6 -> libc-2.6.so
Notice how the first letter of the listing is “l” and the entry seems to have two filenames? This is a special kind of a file called a symbolic link (also known as a soft link or symlink.) In most Unix-like systems it is possible to have a file referenced by multiple names. While the value of this may not be obvious, it is really a useful feature.
注意看，為何這條資訊第一個字元是“l”，並且有兩個檔名呢？ 這是一個特殊檔案，叫做符號連結（也稱為軟連結或者 symlink ）。 在大多數“類別 Unix” 系統中， 有可能一個檔案被多個檔名所指向。雖然這種特性的意義並不明顯，但它真的很有用。
Picture this scenario: a program requires the use of a shared resource of some kind contained in a file named “foo,” but “foo” has frequent version changes. It would be good to include the version number in the filename so the administrator or other interested party could see what version of “foo” is installed. This presents a problem. If we change the name of the shared resource, we have to track down every program that might use it and change it to look for a new resource name every time a new version of the resource is installed. That doesn’t sound like fun at all.
描繪一下這樣的情景：一個程式要求使用某個包含在名為“foo”檔案中的共享資源，但是“foo”經常改變版本號。 這樣，在檔名中包含版本號，會是一個好主意，因此管理員或者其它相關方，會知道安裝了哪個“foo”版本。 這會導致另一個問題。如果我們更改了共享資源的名字，那麼我們必須追蹤每個可能使用了 這個共享資源的程式，當每次這個資源的新版本被安裝後，都要讓使用了它的程式去尋找新的資源名。 這聽起來很沒趣。
Here is where symbolic links save the day. Let's say we install version 2.6 of “foo,” which has the filename “foo-2.6” and then create a symbolic link simply called “foo” that points to “foo-2.6.” This means that when a program opens the file “foo”, it is actually opening the file “foo-2.6”. Now everybody is happy. The programs that rely on “foo” can find it and we can still see what actual version is installed. When it is time to upgrade to “foo-2.7,” we just add the file to our system, delete the symbolic link “foo” and create a new one that points to the new version. Not only does this solve the problem of the version upgrade, but it also allows us to keep both versions on our machine. Imagine that “foo-2.7” has a bug (damn those developers!) and we need to revert to the old version. Again, we just delete the symbolic link pointing to the new version and create a new symbolic link pointing to the old version.
這就是符號連結存在至今的原因。比方說，我們安裝了檔案 “foo” 的 2.6 版本，它的 檔名是 “foo-2.6”，然後建立了叫做 “foo” 的符號連結，這個符號連結指向 “foo-2.6”。 這意味著，當一個程式開啟檔案 “foo” 時，它實際上是開啟檔案 “foo-2.6”。 現在，每個人都很高興。依賴於 “foo” 檔案的程式能找到這個檔案，並且我們能知道安裝了哪個檔案版本。 當升級到 “foo-2.7” 版本的時候，僅新增這個檔案到檔案系統中，刪除符號連結 “foo”， 建立一個指向新版本的符號連結。這不僅解決了版本升級問題，而且還允許在系統中儲存兩個不同的檔案版本。 假想 “foo-2.7” 有個錯誤（該死的開發者！），那我們得回到原來的版本。 一樣的操作，我們只需要刪除指向新版本的符號連結，然後建立指向舊版本的符號連結就可以了。
The directory listing above (from the /lib directory of a Fedora system) shows a symbolic link called “libc.so.6” that points to a shared library file called “libc-2.6.so.” This means that programs looking for “libc.so.6” will actually get the file “libc-2.6.so.” We will learn how to create symbolic links in the next chapter.
在上面列出的目錄（來自於 Fedora 的 /lib 目錄）展示了一個叫做 “libc.so.6” 的符號連結，這個符號連結指向一個 叫做 “libc-2.6.so” 的共享函式庫檔案。這意味著，尋找檔案 “libc.so.6” 的程式，實際上得到是檔案 “libc-2.6.so”。 在下一章節，我們將學習如何建立符號連結。
While we are on the subject of links, we need to mention that there is a second type of link called a hard link. Hard links also allow files to have multiple names, but they do it in a different way. We’ll talk more about the differences between symbolic and hard links in the next chapter.
討論到連結問題，我們需要提一下，還有一種連結型別，叫做硬連結。硬連結同樣允許檔案有多個名字， 但是硬連結以不同的方法來建立多個檔名。在下一章中，我們會談到更多符號連結與硬連結之間的差異問題。
The full version of the Linux Filesystem Hierarchy Standard can be found here:
完整的 Linux 檔案系統層次體系標準可透過以下連結找到：