UNIX file system permissions tutorial - Revision history

Root: /* Acknowlegements */

2007-11-18T14:14:57Z

Acknowlegements

← Older revision		Revision as of 14:14, 18 November 2007
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	This is quite useful in setting up shared folders like <tt>/tmp</tt> (Operating system needs to write many files to <tt>/tmp</tt> as many users. However, other users should not be allowed to delete them at will.)		This is quite useful in setting up shared folders like <tt>/tmp</tt> (Operating system needs to write many files to <tt>/tmp</tt> as many users. However, other users should not be allowed to delete them at will.)

			==Changing permissions of a while directory tree==
			The <tt>-R</tt> option used together with <tt>chmod</tt> can change permissions of a whole directory tree. This can be useful for example when a user wants to grant read access to a whole folder to a group member. This can be achieved by
			<pre>
			chmod g+rx <foldername>
			</pre>
			But, the problem would be, the execute permission. Directories need <tt>x</t>, otherwise they can not be accessed. But, it is not valid to set executable bit (<tt>x</tt>) of a file, unless it is an executable file (e.g. a script, compiled program , etc.). In such situations <tt>X</tt> notation can be useful:
			<pre>
			chmod g+rX foo
			</pre>
			It applies execute permissions to the directory <tt>foo</tt> and all its sub-directories regardless of their current permissions and applies execute permissions to the file under <tt>foo</tt> if only they already have at least 1 execute permission (user, group or others) bit already set.

	==Acknowlegements==		==Acknowlegements==

2006-05-19T00:57:41Z

UNIX filesystem permissoins tutorial moved to UNIX file system permissions tutorial

← Older revision	Revision as of 00:57, 19 May 2006
(No difference)

2006-05-19T00:13:01Z

Sticky Bit

← Older revision		Revision as of 00:13, 19 May 2006
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	When sticky bit is set for a directory by <nowiki>		When sticky bit is set for a directory by <nowiki>
	</nowiki><pre><nowiki>		</nowiki><pre><nowiki>
	#chmod +t /bar #Note: ~~only~~ root ~~can do~~ this		#chmod +t /bar #Note: Usually root does this
	</nowiki></pre> Any file created in that folder can be removed only by creator, even if others have write permission in the folder.		</nowiki></pre> Any file created in that folder can be removed or moved only by creator, even if others have write permission in the folder.

	This is quite useful in setting up shared folders like <tt>/tmp</tt> (Operating system needs to write many files to <tt>/tmp</tt> as many users. However, other users should not be allowed to delete them at will.)		This is quite useful in setting up shared folders like <tt>/tmp</tt> (Operating system needs to write many files to <tt>/tmp</tt> as many users. However, other users should not be allowed to delete them at will.)

2006-05-19T00:09:06Z

Checking umask

@@ Line 170: / Line 170: @@
 </nowiki><pre><nowiki>umask 0022</nowiki></pre> and <nowiki>
 </nowiki><pre><nowiki>u=rwx,g=rx,o=rx</nowiki></pre>, respectively.
 ==Acknowlegements==

2006-05-18T23:42:03Z

umask Unmasked

← Older revision		Revision as of 23:42, 18 May 2006
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	Some common umask settings in a more understandable way. <nowiki>		Some common umask settings in a more understandable way. <nowiki>
	</nowiki><pre><nowiki>		</nowiki><pre><nowiki>
	umask ~~file~~ ~~dirs~~ files dirs		umask dirs files files dirs
	022 759 648 -rw-r--r-- drwxr-xr-x		022 759 648 -rw-r--r-- drwxr-xr-x
	027 754 643 -rw-r----- drwxr-x---		027 754 643 -rw-r----- drwxr-x---

2006-05-01T13:04:55Z

← Older revision		Revision as of 13:04, 1 May 2006
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			[[Image:DSC_0063.JPG\|thumb\|450px]]
	==Checking and Understanding Permissions==		==Checking and Understanding Permissions==

2006-04-05T04:18:45Z

Setting default file permissions

← Older revision		Revision as of 04:18, 5 April 2006
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	== Setting default file permissions ==		== Setting default file permissions ==
	{{box\|See [[wikipedia:Bash#Bash_startup_scripts\|this article]] on ~~startup scripts~~ of bash shell}}		{{box\|See [[wikipedia:Bash#Bash_startup_scripts\|this article]] on initialization files of bash shell}}
	When a user creates a file or a directory, the initial permissoins of those are determined by the 'uname' value which is set by		When a user creates a file or a directory, the initial permissoins of those are determined by the 'uname' value which is set by
	# '''uname''' command		# '''uname''' command

2006-04-04T23:36:54Z

umask Unmasked

← Older revision		Revision as of 23:36, 4 April 2006
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	==umask Unmasked==		==umask Unmasked==
			{{wbox\|Never take the umask command lightly! If you accidentally set umask 002, every single file you (or any of your programs!) create after that will be writable by everybody in your group!!}}
	umask is a [[wikipedia:octal number\|ocatal number]] between 000 and 777, directly affecting the resulting file and directory permissions. The three numbers from left, governs the permissions for user, group and others respectively. Each number relates to the respective chmod value as follows. <nowiki>		umask is a [[wikipedia:octal number\|ocatal number]] between 000 and 777, directly affecting the resulting file and directory permissions. The three numbers from left, governs the permissions for user, group and others respectively. Each number relates to the respective chmod value as follows. <nowiki>
	</nowiki><pre><nowiki>		</nowiki><pre><nowiki>

2006-04-04T23:34:08Z

umask Unmasked

← Older revision		Revision as of 23:34, 4 April 2006
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	7 0 0		7 0 0
	</nowiki></pre>		</nowiki></pre>

	~~Some common umask settings in a more understandable way.~~
	{{box\|The results shown in the table can be obtained from [[File_permission_demonstration_script\|this bash script]]. }}		{{box\|The results shown in the table can be obtained from [[File_permission_demonstration_script\|this bash script]]. }}
			Some common umask settings in a more understandable way. <nowiki>
	<pre>		</nowiki><pre><nowiki>
	umask file dirs files dirs		umask file dirs files dirs
	022 759 648 -rw-r--r-- drwxr-xr-x		022 759 648 -rw-r--r-- drwxr-xr-x
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	007 770 659 -rw-rw---- drwxrwx---		007 770 659 -rw-rw---- drwxrwx---
	077 714 603 -rw------- drwx------		077 714 603 -rw------- drwx------
	</pre>		</nowiki></pre>

	===Checking umask===		===Checking umask===

2006-04-04T23:33:26Z

umask Unmasked

← Older revision		Revision as of 23:33, 4 April 2006
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	==umask Unmasked==		==umask Unmasked==
	umask is a [[wikipedia:octal number\|ocatal number]] between 000 and 777, directly affecting the resulting file and directory permissions. The three numbers from left, governs the permissions for user, group and others respectively. Each number relates to the respective chmod value as follows. <nowiki>		umask is a [[wikipedia:octal number\|ocatal number]] between 000 and 777, directly affecting the resulting file and directory permissions. The three numbers from left, governs the permissions for user, group and others respectively. Each number relates to the respective chmod value as follows. <nowiki>
	</nowiki><pre><nowiki~~>ha</nowiki></pre>~~		</nowiki><pre><nowiki>
	~~<pre~~>
	umask File Directory		umask File Directory
	0 6 7		0 6 7
Line 144:		Line 143:
	6 0 1		6 0 1
	7 0 0		7 0 0
	</pre>		</nowiki></pre>

	Some common umask settings in a more understandable way.		Some common umask settings in a more understandable way.
	{{box\|The results shown in the table can be obtained from [[File_permission_demonstration_script\|this bash script]]. }}		{{box\|The results shown in the table can be obtained from [[File_permission_demonstration_script\|this bash script]]. }}