• - indicates it is a file.
• rwx indicates that the file owner has permissions to read, write, and execute the file.
• rw- indicates that the group has permissions to read and write, but not execute the file.
• --- indicates that other users have no permission to read, write, or execute the file.
• . indicates that the SELinux security context is set for the file.

• d indicates it is a directory.

• rwx indicates that the directory owner has the permissions to read, write, and access the contents of the directory.

  As a directory owner, you can list the items (files, subdirectories) within the directory, access the content of those items, and modify them.

• r-- indicates that the group has permissions to read, but not write or access the contents of the directory.

  As a member of the group that owns the directory, you can list the items within the directory. You cannot access information about the items within the directory or modify them.

• --- indicates that other users have no permission to read, write, or access the contents of the directory.

  As someone who is not an user owner, or as group owner of the directory, you cannot list the items within the directory, access information about those items, or modify them.

• . indicates that the SELinux security context is set for the directory.

• Read (r).
• Write (w).
• Execute (x).

• User owner (u).
• Group owner (g).
• Other (o).
• All (a).

• + to add the permissions on top of the existing permissions.
• - to take away the permissions from the existing permission.
• = to omit the existing permissions and explicitly define the new ones.

Procedure

• To change the file permissions for an existing file or directory, use:

  $ chmod u=symbolic_value,g+symbolic_value,o-symbolic_value file-name

  Replace file-name with the name of the file or directory, and replace symbolic_value for user, groups, and others with corresponding symbolic values. See Section 5.1.1, “Base permissions” for more details.

  Example

  To change file permissions for my-file.txt from 664 (-rw-rw-r--) to 740 (-rwx-r---), use:

  $ chmod u+x,g-w,o= my-file.txt

  Note that any permission that is not specified after the equals sign (=) is automatically prohibited.

• To set the same permissions for user, group, and others, use:

  $ chmod a=symbolic_value file-name

  Replace file-name with the name of the file or directory, and replace symbolic_value with a symbolic value. See Section 5.1.1, “Base permissions” for more details.

  Example

  To set the permission for my-file.txt to 777 (-rwxrwxrwx or drwxrwxrwx), use:

  $ chmod a=rwx my-file

• To change the permissions for a directory and all its sub-directories, add the -R option:

  $ chmod -R symbolic_value directory-name

  Replace directory-name with the name of the directory, and replace symbolic_value with a symbolic value. See Section 5.1.1, “Base permissions” for more details.

  Example

  To change the permissions for /my-directory/ and all its sub-directories from 775 (drwxrwxr-x) to 740 (drwx-r---), use:

  $ chmod -R g-wx,o= /my-directory

Procedure

• To change the file permissions for an existing file or directory, use:

  $ chmod octal_value file-name

  Replace file-name with the name of the file or directory, and replace octal_value with an octal value. See Section 5.1.1, “Base permissions” for more details.

Procedure:

• To display the current octal value of the umask for a standard user, use:

  $ umask

• To display the current octal value of the umask for a root user, use:

  $ sudo umask

  Or:

  # umask

Procedure

• To display the current symbolic value of the umask, use:

  $ umask -S

• To display the current symbolic value of the umask for a root user, use:

  $ sudo umask -S

  Or:

  # umask -S

Procedure

• To display the default bash umask for the non-login shell, use:

  $ grep umask /etc/bashrc

  The output returns:

  # By default, we want umask to get set. This sets it for non-login shell.
         umask 002
         umask 022

• To display the default bash umask for the login shell, use:

  $ grep umask /etc/profile

  The output returns:

  # By default, we want umask to get set. This sets it for login shell
         umask 002
         umask 022

Procedure

• To set or remove permissions for the current shell session, you can use minus (-), plus (+), and equals (=) signs in combination with symbolic values.

  $ umask -S u=symbolic_value,g+symbolic_value,o-symbolic_value

  Replace symbolic_value for user, group, and others with symbolic values. See Section 5.1.2, “User file-creation mode mask” for more details.

  Example

  If your current umask is set to 113 (u=rw-,g=rw-,o=r--) and you want to set it to 037 (u=rwx,g=-r-,o=---), use:

  $ umask -S u+x,g-w,o=

  Note that any permission that is not specified after the equals sign (=) is automatically prohibited.

• To set the same permissions for user, group, and others, use:

  $ umask a=symbolic_value

  Replace symbolic_value with a symbolic value. See Section 5.1.2, “User file-creation mode mask” for more details.

  Example

  To set the umask to 000 (u=rwx,g=rwx,o=rwx), use:

  $ umask a=rwx

Procedure

• To set the umask for the current shell session using octal values, use:

  $ umask octal_value

  Replace octal_value with an octal value. See Section 5.1.2, “User file-creation mode mask” for more details.

Procedure

• Put the line that specifies the octal value of the umask into the .bashrc file for the particular user.

  $ echo 'umask octal_value' >> /home/username/.bashrc

  Replace octal_value with an octal value and replace username with the name of the user. See Section 5.1.2, “User file-creation mode mask” for more details.

Procedure

• To display the current ACL for a particular file or directory, use:

  $ getfacl file-name

  Replace file-name with the name of the file or directory.

Prerequisites

• Root access

Procedure

• To set the ACL for a file or directory, use:

• Not executable by anyone.
• The user andrew has the rw- permission.
• The user susan has the --- permission.
• Other users have the r-- permission.

Verification steps

• To verify that the user andrew has the rw- permission, the user susan has the --- permission, and other users have the r-- permission, use:

  $ getfacl group-project

  The output returns:

  # file: group-project
  # owner: root
  # group: root
  user:andrew:rw-
  user:susan:---
  group::r--
  mask::rw-
  other::r--