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|<code>/</code>
|theThe slash <code>/</code> character alone denotes the root of the virtual filesystem tree.
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:<code>/bin</code>
|standsStands for "[[computer program|binaries]]" and contains certain fundamental utilities, such as <code>ls</code> or <code>cp</code>, which are generally needed by all users.
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:<code>/sbin</code>
|standsStands for "[[computer program|system (or "superuser") binaries]]" and contains fundamental utilities, such as <code>init</code>, usually needed to start, maintain and recover the system.
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:<code>/etc</code>
|containsContains system-wide configuration files and system databases.
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:<code>/dev</code>
|standsStands for "devices". Contains [[device node|file representations]] of peripheral devices.
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::<code>[[/dev/null]]</code>
|alsoAlso known as the "bit bucket" or "black hole", this [[pseudo-device]] discards all contents written to it, and is typically used to pipe away unwanted data.
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::<code>[[/dev/random]]</code>
|thisThis pseudo-device returns [[pseudorandom numbers]] (subject to the limitations of [[random number generator]]s in [[computing]]) when read from. It uses system noise to generate random numbers and blocks if not enough entropy in the noise is available. Random is commonly used by programs such as [[Secure Shell|SSH]] that absolutely need cryptographically strong random data to generate an [[encryption]] key.
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::<code>/dev/urandom</code>
|similarSimilar to <code>/dev/random</code>, except it always returns (cryptographically less strong) pseudorandom numbers, even if there is not enough entropy in the system noise available.
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:<code>/home</code>
|containsContains the home directories for the users.
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:<code>/mnt</code>
|containsStands for "mount". Contains filesystem mount points.
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:<code>/lib</code>
|containsContains system libraries.
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:<code>/root</code>
|The home directory for the [[superuser]] root. This account's home directory is usually on the initial filesystem (and hence not in /home) in case specific maintenance needs to be performed, during which other filesystems are not available. Such a case could occur, for example, if a hard disk drive suffers physical failures and cannot be properly mounted.
|the home directory for the [[superuser]] root.
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:<code>/tmp</code>
|aA place for temporary files. Many Unices clear this directory upon start up.
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:<code>/usr</code>
|originallyOriginally the directory holding user home directories, its use has changed, and. itIt now holds executables, libraries, and shared resources that are not system critical, like the [[X Window System]], [[KDE]], [[Perl]], etc. (The name "Unix System Resources" is a ''post hoc'' [[backronym]]{{citation needed|date=December 2010}}.) However, on some [[Unix]] systems, some user accounts may still have a home directory that is a direct subdirectory of /usr, such as the default as in [[Minix]]. (these user accounts are often related to server or system use, and not directly used by a person)
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::<code>/usr/bin</code>
|thisThis directory stores all binary programs distributed with the operating system not residing in <code>/bin</code>, <code>/sbin</code> or (rarely) <code>/etc</code>.
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::<code>/usr/include</code>
|storesStores the development headers used throughout the system. Header files are mostly used by the <code>#include</code> directive in [[C programming language]], which is how the name of this directory was chosen.
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::<code>/usr/lib</code>
|storesStores the required libraries and data files for executablesprograms stored within <code>/usr</code> or elsewhere.
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::<code>/usr/local</code>
|resemblesResembles <code>/usr</code>, except that its subdirectories are used for additions not part of the operating system distribution, such as custom programs or files from a [[BSD]] [[Ports collection]]. Usually has subdirectories such as <code>/usr/local/lib</code> or <code>/usr/local/bin</code>.
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:<code>/var</code>
|aA short for "variable." A place for files that may change often, for example e-mail sent to users on the system, or process-ID [[lock file]]s.
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::<code>/var/log</code>
|containsContains system log files.
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::<code>/var/mail</code>
|theThe place where all the incoming mails are stored. TheUsers (other userthan <code>root</code>) can access his/hertheir own mail only, unless he/she has admin rights.
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::<code>/var/spool</code>
|[[spooling|spoolSpool]] directory;. containsContains print jobs, mail spools and other queued tasks.
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::<code>/var/tmp</code>
|A place for temporary files which should be preserved between system reboots.
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:<code>/proc</code>
|Contains all processing data (process information about a running operating system). Usually, the entire contents of this directory is created on-the-fly by the operating system's kernel when it is read by a process; it does not actually exist on disk. The contents reflects the current and immediate state of the system and all processes running on it. There is normally a special filesystem of type "proc" mounted here (or "none" on some systems) as shown by the "mount" command.
|contains all processing data (process information about a running operating system).
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:<code>/opt</code>
|Contains add-on software. Some large program suites may prefer to be installed here, rather than under <code>/usr</code>.
|contains add-on software.
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:<code>/media</code>
|defaultDefault mount point for removable devices, such as USB sticks, media players, etc.
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:<code>/srv</code>
|serverServer data (data for services provided by system).
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:<code>/boot</code>
|containsContains all the important files which are required for successful booting process.
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:<code>/sys</code>
|containsContains information related to hardware. See <code>/proc</code> above.
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