Question

2. [5] What is the command used to limit the default permissions for new file and new directory? Please write the command to set the default file permission to -rw- and default directory permission to drwx--x-x

Answer 1

Answer 2 :

umask is the command that is used for setting the default permission for new file and new directory. umask set the permission in the terminal you are currently working , if you want to change the umask value permanently then you need to change your ~/.bashrc file.

uname 066 is the command to set the default file permission to -rw------- and default directory permission to drwx--x--x.

Explanation:

for example:

umask 002 , if we are using the umask value in numeric form (in numeric form value for  read permission is 4, for write is 2 and for execute is 1) these values gets subtracted from 666 when a file is created and from 777 when a directory is created. In numeric first number is to give permission to user and second is to give permission to group and third number is to permission for others(any one else). for example: after running umask 002, if we create a file then it will have permission 664 i.e. user and group have the read and write permission while other has read permission only. In numeric for, by default execution permission is not provided to the file.

There is another way we can set the umask value, by using the symbols(abbreviations) , r for read , x for execute, w for write, u for user, g for group, o for other.

for example : umask u=rwx,g=rw,o=r

in this for we are providing the permission values i.e if we create a file or directory, then user(owner) can read write and execute the file and groups can read and write while others can just read. these values should be comma separated, spaces are not allowed.

in another way, example: umask u+x,g+r,o-w
in this for what , umask take the original permissions set by operating system and + (means add) or -(means remove) the permission for file and directories. in this example, we are adding the execution permission to user and adding read permission to group and removing the write permission for other. Other default permission remains same.

in symbolic for these permission are applied for both files and directories