How to set permissions for folder in Unix/Linux Ubuntu

Question

This is not necessarily direct computer science question but its closely related.

Is there any way to do this.

I am using Z Shell zsh.

I want to set up so whenever i am in folder

~/blah

Everything I create is created using permissions 770 (All access wrx for me and group). Basically whatever I do in that folder should have those permissions.

In addition group for that file should be done in same way. But thats same process as the one for the permissions.

Anyone?

Answer 1

Found a nice article on this subject: What is the "umask"? How can I set it?

The umask defines the permissions a new file will get - or better: the permissions it will not get.

[...]

If you want to define the umask for a specific directory (example: group write permissions for a directory you use together with your colleges), you'll become sweating when using the umask command because it is always valid for all directories.

The solution of this problem is setting a default ACL. The following command ensures that all new files in /home/shared/ have all permissions (including write permissions) set for the group:

setfacl -d -m mask:007 /home/shared/

You should also set the sgid-bit for the directory and choose the wanted group using chgrp:

chgrp the_team /home/shared/
chmod g+s /home/shared/

If /home/shared/ already contains subdirectories, you have to change their permissions as well. Tip: all mentioned commands know the -R option.

Answer 2

Set

umask 006

in your ~/.bash_profile which is different from the default of 022. Also set

chgrp staff         # or some other group you pick
chmod g+s blah

to enable the sticky bit on the directory. Now everything you create below it should retain the modes as well as the group.

Answer 3

Don't forget that the filesystem must be mounted with the 'acl' flag in order to use access control lists. Otherwise the setfacl command will return 'Operation not supported'.

For example this is the entry in my fstab file (/etc/fstab):-

# <file system>  <mount point>     <type>  <options>   <dump>  <pass>
/dev/sdb1        /media/DataDrive  ext3    acl         0       0

Answer 4

You can define a chpwd() function which will be run every time the cwd of the shell is changed. Inside there, test the directory and set umask appropriately.

function chpwd {
  [[ $PWD == $HOME/blah ]] && { umask 007; return }
  # or, if more tests here, use case $PWD in ... esac
  umask 022
}

Answer 5

umask will change the default permissions for a every file and directory you will create, but if you need this behavior to be only for a given directory you should look at access control lists ACLs see: man acl(5) for more information.