chmod g-rx mydir/
removes read and execute permissions from group. It will leave intact any permissions for other (everyone), and write permissions for group.
It is different to:
chmod a-rx mydir/
chmod u+rx mydir/
a-rx impacts all three rights. It still leaves write permissions in place however for group or other.
The best way to do it is to set all permissions explicitly:
chmod 0700 mydir/
The 7 is binary for 111, where each bit represents read, write and execute respectively, at that position, refers to user (the file owner). The four positions in the
0700 refer to
group permissions and
other permissions respectively.
Use this to help translate between the number associated with rights, and the read, write, execute flags.