Is it normal that all the folders I create are set to 775

Question

I am getting to know linux little by little. I have just set up a new server and I see some behavior that I am not really used to. I have worked with servers before, that were not owned by me, and I have not seen this.

Basically, the folders that I create are automatically set to 775, and the files I create are set to 755.

On the servers I used to work with everything is set to 664 I think.

Now can I change this behavior, and more important, do I need to change this behavior. For now I am the only one using this server. The ports are all non-standard, and root logins are disabled.

Answer 1

Umask explained

The default file permissions on newly created files and directories are a standard permission (rw-rw-rw for files, rwxrwxrwx for directories) subtracting the current umask setting. A umask setting of 000 would keep the standard permissions, whereas a setting of 777 would remove all permissions.

The three numbers in the umask represent user, group and anyone permissions respectively. The number represents three binary digits whether to remove a specific permission or not.

d - rwx
-------
0 - 000 (rwx)
1 - 001 (rw-)
2 - 010 (r-x)
3 - 011 (r--)
4 - 100 (-wx)
5 - 101 (-w-)
6 - 110 (--x)
7 - 111 (---)

To calculate which permissions a new file will have given a certain umask, start with the default permission and subtract the umask.

orig    rwx rwx rwx (777, default directory permission)
umask   000 010 010 (022)
result  rwx r-x r-x (755)

orig   rw- rw- rw- (666, default file permission)
umask  000 010 010 (022)
result rw- r-- r-- (644)

orig   rwx rwx rwx (777, default directory permission)
umask  000 000 010 (002)
result rwx rwx r-x (775)

orig   rw- rw- rw- (666, default file permission)
umask  000 000 010 (002)
result rw- rw- r-- (664)

Answer 2

That is defined by the "umask". You can have a look here for an explanation.