January 2018
Intermediate to advanced
376 pages
8h 45m
English
Content preview from Mastering Linux Security and Hardening
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Setting permissions with the numerical method
With the numerical method, you'll use an octal value to represent the permissions settings on a file or directory. To the r, w, and x permissions, you assign the numerical values 4, 2, and 1, respectively. Do this for the user, group, and others positions, and add them all up to get the permissions value for the file or directory:
| User | Group | Others |
| rwx | rwx | rwx |
| 421 | 421 | 421 |
| 7 | 7 |
7 |
So, if you have all the permissions set for everybody, the file or directory will have a value of 777. If I were to create a shell script file, by default, it would have the standard 664 permissions, meaning read and write for the user and group, and read-only for others:
-rw-rw-r--. 1 donnie donnie 0 Nov ...
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