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--- linux_wiki:list_set_and_change_standard_ugo_rwx_permissions [2016/02/28 22:58]
billdozor created
+++ linux_wiki:list_set_and_change_standard_ugo_rwx_permissions [2019/05/25 23:50] (current)
@@ Line 3: / Line 3: @@
 **General Information**
-About this page/how-to/script.
+Ownership and permissions.
 ----
@@ Line 43: / Line 43: @@
 ===== Change Permissions =====
-=== Symbolic ===
+==== Symbolic ====
   * u => user owner
@@ Line 67: / Line 67: @@
   * For user owner and group => Adds execute to dir1 and all sub directories, not files.
-=== Octal ===
+----
+==== Octal ====
   * 4 => read
@@ Line 81: / Line 83: @@
   * group => read(4) permissions
   * others => no(0) permissions
+----
+===== Setuid, Setgid, sticky bits =====
+  * Setuid => execute file with owner's permissions
+  * Setgid => execute file with group's permissions (most often set on directories to keep files created in that dir owned by the group)
+  * Sticky bit => when set on a directory, prevents file deletion unless the user is the owner. (even if they have write permissions)
+Add setuid to script1
+<code bash>
+chmod u+s script1
+</code>
+\\
+Same scenario, octal mode
+<code bash>
+chmod 4740 script1
+</code>
+When there are four numbers in chmod, the first is for setuid/gid/stickybit:
+  * 4 => setuid
+  * 2 => setgid
+  * 1 => sticky bit
+----
+===== umask: default file/directory permissions =====
+  * umask permissions are "masking" the permissions that we don't want to have.
+  * New files will **not** be created with execute permissions by default.
+  * New directories **will** be created with execute permissions by default.
+View current defaults
+<code bash>
+umask
+</code>
+  * Defaults show above are in octal
+  * Owner => 0 (don't mask any)
+  * Group => 2 (mask write permissions)
+  * Others => 2 (mask write permissions)
+\\
+The above yields a file with the following permissions by default:
+<code bash>
+-rw-r--r--   1 user user    0 Jun 22 14:01 file1
+</code>
+\\
+Temporarily change the default for this session only
+<code bash>
+umask 266
+touch testfile
+ls -l
+dr-x--x--x   2 user user 4096 Jun 22 14:09 testdir
+-r--------   1 user user    0 Jun 22 14:08 testfile
+</code>
+\\
+Permanent umask changes (system wide)
+<code bash>
+vim /etc/bashrc
+vim /etc/profile
+if [ $UID -gt 199 ] && [ "`id -gn`" = "`id -un`" ]; then
+       umask 002
+    else
+       umask 022
+fi
+</code>
+  * User accounts with a user id greater than 199 and the group name is the same as their username => umask of 002.
+  * All other users => umask of 022
+  * Note: Need to make this change in /etc/bashrc and /etc/profile
 ----