The chmod command is used to change the permissions of files and directories. The permissions are represented by three sets of three characters, indicating the permissions for the owner, the group, and the others. Each character can be either r (read), w (write), x (execute), or - (no permission). The chmod command can use either symbolic or numeric mode to specify the permissions. In this question, the numeric mode is used, which consists of three digits from 0 to 7. Each digit is the sum of the permissions for each set, where r is 4, w is 2, and x is 1. For example, 7 means rwx, 6 means rw-, and 4 means r–. Therefore, the command chmod 654 file.txt sets the permissions as follows:
The first digit 6 means rw- for the owner, which means the owner can read and write the file, but not execute it.
The second digit 5 means r-x for the group, which means the group can read and execute the file, but not write it.
The third digit 4 means r-- for the others, which means the others can only read the file, but not write or execute it.
The resulting permissions are -rw-r-xr–, which is the correct answer. The other options are incorrect because they either have the wrong permissions or the wrong file type. A regular file does not have the d (directory) prefix, and a directory cannot have the - (no file type) prefix. References:
Linux Essentials Version 1.6 Objectives: 4.1. Ownership and Permissions1
Linux Essentials Version 1.6 Exam Study Resources: Linux Essentials Manual - Chapter 8. Security and File Permissions - 8.1. Ownership and Permissions - 8.1.1. The chmod Command2
Linux Essentials Version 1.6 Exam Study Resources: Linux Essentials Manual - Appendix A. Answers to the Exercises - Chapter 8. Security and File Permissions - 8.1. Ownership and Permissions - Exercise 8.1.12
