[support] Permissions of ~/.drush/cache/default

[Kenneth Jacker]

Running "drush update" on a multisite included this line in its output:

  /home/khj/.drush/cache/default exists,  [error]
  but is not writable. 
  Please check directory permissions.

The permissions are currently 775.  FWIW, files *were* successfully
created there after the "update" ...

Should I change the permissions?  To what?

Thanks,

  -Kenneth