File permission

chattr

https://www.computerhope.com/unix/chattr.htm#list-of-attributes

• lsattr <file>

  list file attribute

  # output example
  ----i-------- /etc/resolv.conf
  
  # some attributes:
  a: append mode only for writing
  i: immutable (cannot be deleted or renamed, `sudo rm -f` will show `Operation not permitted`, but not `Permission denied` )
  

• chattr [-R] [+/-/=<attr>] <file>

  change the attributes of file or directory.

chown

change ownership of file or directory.

only root can use chown.

similarly, there is chgrp for change group of file or directory.

sudo chown <new-owner> <file>
sudo chown <new-owner:new-group> <file>
sudo chown -R <new-owner> <dir>

umask

set/check default user permission mask for new files.

umask # show current default umask
umask 022 # rw-r--r--

# u[ser], g[roup], o[ther], a[ll]
umask a= # dangerous! ---------
umask u+x # rwxr--r--

chmod

set user permission mask for a specific file.

chmod 777 <file> # rwxrwxrwx
chmod u=rwx,g=rx,o=r <file>

chmod -R 777 <dir>

note the escaped space!

`python\ ` looks the same as `python ` in default ls and top.
but `ls --escape` will reveal it!