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--- linux_wiki:list_set_and_change_standard_ugo_rwx_permissions [2016/02/29 23:00]
billdozor [Setuid, Setgid, sticky bits]
+++ linux_wiki:list_set_and_change_standard_ugo_rwx_permissions [2019/05/25 23:50]
@@ Line 1: / Line 1: @@
-====== List Set And Change Standard Ugo Rwx Permissions ======
-**General Information**
-Ownership and permissions.
-----
-====== Permissions Overview ======
-Permissions tools
-  * chmod => Change permissions for user, group, other, or all
-  * chown => Change user/group ownership
-Chmod Modes
-  * symbolic => represent permissions via u,g,o,a
-  * octal => represent permissions with numbers
-Change file1 ownership to rjones and group to student
-<code bash>
-chown rjones:student file1
-</code>
-  * You can leave off either the username or group name if only changing one of them, but the colon (:) must remain if only changing the group owner.
-----
-===== List Permissions =====
-<code bash>
-ls -l
--rw-r--r--. 2 root root          0 Jun 20 15:11 file1
--rw-r--r--. 2 root root          0 Jun 20 15:11 file2
-drwxr-xr-x. 3 root root         17 Jun 20 14:50 newdir
-</code>
-  * First column => - (file), d (directory, l (symlink)
-  * Columns 2-4 => User owner permissions (rwx)
-  * Columns 5-7 => Group permissions (rwx)
-  * Columns 8-10 => Other permissions (rwx)
-----
-===== Change Permissions =====
-==== Symbolic ====
-  * u => user owner
-  * g => group
-  * o => other users
-  * a => all users
-Add write permissions to a file for the group
-<code bash>
-chmod g+w file1
-</code>
-Take away read permissions for others, for all of dir1 directory and its contents
-<code bash>
-chmod -R o-r dir1
-</code>
-  * -R => recursively
-Add execute permissions to directories only in a tree
-<code bash>
-chmod -R ug+X dir1
-</code>
-  * For user owner and group => Adds execute to dir1 and all sub directories, not files.
-----
-==== Octal ====
-  * 4 => read
-  * 2 => write
-  * 1 => execute
-  * Add together to get permissions
-Set file1 permissions using octal notation
-<code bash>
-chmod 740 file1
-</code>
-  * user owner => read(4),write(2),execute(1) permissions (4+2+1=7)
-  * 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
-----