Unix File System Permissions
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Unix File System Permissions

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Questions and Answers

What is the default group ownership of a file created by a user?

  • The root group
  • The user's secondary group
  • A random group
  • The user's primary group (correct)

    • The userdel command is used to add a user to a group.

    False

    What command is used to create a new user?

    useradd

    The file ________ contains all user details as a list.

    <p>/etc/passwd</p> Signup and view all the answers

    What flag is used with the usermod command to add a user to a group?

    <p>-aG</p> Signup and view all the answers

    The groupdel command is used to add a group.

    <p>False</p> Signup and view all the answers

    Match the following commands with their functions:

    <p>useradd = Create a new user usermod = Modify user attributes userdel = Delete a user account groupadd = Create a new group groupdel = Delete a group</p> Signup and view all the answers

    What command is used to change the group ownership of a file or directory?

    <p>chown</p> Signup and view all the answers

    What does the permission 'rw-' indicate?

    <p>The group has read and write permissions, but not execute</p> Signup and view all the answers

    The 'chown' command is used to change the permissions of a file.

    <p>False</p> Signup and view all the answers

    What is the command used to change the permissions of a file?

    <p>chmod</p> Signup and view all the answers

    Each file has a primary user that owns it and a ______________ assigned to it.

    <p>group</p> Signup and view all the answers

    What is the effect of setting the permissions to 700?

    <p>The file is visible only to the username and no one else</p> Signup and view all the answers

    Match the following commands with their functions:

    <p>chmod = Change the permissions of a file chown = Change the ownership of a file chgrp = Change the group of a file mkdir = Create a new directory</p> Signup and view all the answers

    The root user has limited privileges in Linux.

    <p>False</p> Signup and view all the answers

    What is the purpose of groups in Linux?

    <p>To simplify access control and permissions management</p> Signup and view all the answers

    What is the purpose of user and group management in Linux?

    <p>To maintain security and access control</p> Signup and view all the answers

    The /etc/gshadow file contains all user accounts details as a list.

    <p>False</p> Signup and view all the answers

    What is the purpose of the 'chage' command in Linux?

    <p>To manage password policies and measures</p> Signup and view all the answers

    The password inactive date is the deadline for using an expired password, after the deadline the user account will be ______________________ if the expired password is not changed.

    <p>locked</p> Signup and view all the answers

    What is the purpose of file system permissions in Unix?

    <p>To control the ability of user and group accounts to read, modify, and execute files</p> Signup and view all the answers

    The numerical value 777 for a directory grants only the owner full permissions.

    <p>False</p> Signup and view all the answers

    What is the purpose of password expiration date?

    <p>To specify the last date the password remains valid</p> Signup and view all the answers

    Match the following password aging policy settings with their descriptions:

    <p>Last password change date = The date when the last password has been changed by the user Password expiration date = The last date the password remains valid, after the last date the password is no longer valid Account expiration date = The deadline for the user will be able to use an account, after the deadline the account will be automatically locked Minimum number of days between password change = The number of days before the user is allowed to rechange the password</p> Signup and view all the answers

    What is the meaning of the numerical value 755 for file permissions?

    <p>Owner/User has full permissions, Group has read and execute permissions, and Other/Everyone has read and execute permissions</p> Signup and view all the answers

    A file with permissions $ ls -l –rwxrw- - - -. indicates that the file owner has permissions to ______________ the file.

    <p>read, write, and execute</p> Signup and view all the answers

    The /etc/login.defs file is used to manage user accounts in Linux.

    <p>False</p> Signup and view all the answers

    What is the permission level of 0 in numerical value?

    <p>No access to the file whatsoever</p> Signup and view all the answers

    What is the purpose of sending a warning message to users to change the password?

    <p>To give users a reminder to change their password before it expires</p> Signup and view all the answers

    The permission level of 7 in numerical value means read and write permissions only.

    <p>False</p> Signup and view all the answers

    Match the following numerical values with their corresponding permission levels:

    <p>0 = No access to the file whatsoever 1 = Execute permissions only 4 = Read permissions only 7 = Read, write, and execute permissions (full permissions)</p> Signup and view all the answers

    Study Notes

    File/Folder Permissions and Ownership

    • File system permissions control the ability of user and group accounts to read, modify, and execute the contents of files and to enter directories.
    • Three types of access (permissions): read (r), write (w), execute (x).
    • Each file belongs to a specific user and group (ownership).
    • Access to files is controlled by user (u), group (g), and other/everyone (o) permission bits, usually set using a numerical value.

    Access Levels and Permissions

    • Different access levels depending on numerical values:
      • 0 (---) – no access to the file whatsoever
      • 1 (--x) – execute permissions only
      • 2 (-w-) – write permissions only
      • 3 (-wx) – write and execute permissions
      • 4 (r--) – read permissions only
      • 5 (r-x) – read and execute permissions
      • 6 (rw-) – read and write permissions
      • 7 (rwx) – read, write, and execute permissions (full permissions)

    Directory Permissions

    • Base permission for a directory is 777 (drwxrwxrwx), which grants everyone the permissions to read, write, and execute.
    • Example of 644 permissions:
      • Owner/User: Read and Write
      • Group: Read only
      • Other/Everyone: Read only

    Setting Permissions and Ownership

    • To set permissions, use the chmod command followed by the permission value and the file name.
    • Example: chmod 755 file_name sets the permissions to 755 for the file file_name.
    • To recursively change permissions, use the -R flag: chmod -R 755.
    • To change ownership, use the chown command followed by the user and group names, and the file name.
    • Example: chown user:siteground file_name sets the owner to user and the group to siteground.

    Understanding Users and Groups

    • In Linux, a user is an individual who interacts with the system, with a unique username and user ID (UID).
    • User accounts are used to log in, run processes, and access files and directories.
    • Groups are collections of users, used to simplify access control and permissions management.
    • A group has a unique group ID (GID).

    User Management

    • Creating users: use the useradd command followed by the username.
    • Example: sudo useradd viswa creates a new user named viswa.
    • Setting user password: use the passwd command followed by the password.
    • Modifying user attributes: use the usermod command.
    • Deleting users: use the userdel command with the -r flag to remove the user and their home directory.

    Group Management

    • Creating groups: use the groupadd command followed by the group name.
    • Example: sudo groupadd mygroup creates a new group named mygroup.
    • Adding users to groups: use the usermod command with the -aG flag.
    • Example: sudo usermod -aG mygroup username adds the user to the mygroup group.
    • Changing group ownership of files: use the chown command with the group name.
    • Deleting groups: use the groupdel command followed by the group name.

    Group Database Files

    • /etc/group contains all group details as a list.
    • /etc/gshadow contains all group members details as a list.

    Password Aging Policy

    • To ensure system and network security, various security mechanisms are used, including user password expiration.
    • The chage command and /etc/login.defs file are used to manage password policies.
    • Password aging policy settings include:
      • The last password change date
      • The password expiration date
      • The password inactive date
      • The account expiration date
      • The minimum number of days between password changes
      • The maximum number of days between password changes
      • The number of days of warning before the password expires

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    Description

    Learn about Unix file system permissions and how they control access to files and directories. Understand read, write, and execute permissions, as well as file ownership.

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