chmod go-r doesn't remove write permissions, it removes read permissions. The contents of
/ is primarily directories; on directories read permission means you're allowed to list it. E.g.,
ls /bin will now give a permission denied (except for the directory owner and root, of course the owner is root in this case).
If that was a typo and you meant
chmod go-w, then you indeed removed write permission. Likely the only directory which had write permission for group or other was
/tmp; you need to fix that.
Thankfully, you didn't include
-R (recursive) in your
chmod, so this is fairly easy to fix: Just compare
ls -l / on the test server to
ls -l / on a similar server. Use
chmod to set the permissions back as they should be.
Note that chmod will follow symlinks, so if you have any in your root directory, you'll need to confirm them separately.
Finally, you don't appear to understand the Unix permissions model. Each file and directory has one user (the owner) and one group. The owner can have read, write, and/or execute permissions on the file/directory. That's what
chmod u=... sets. All members of the group can have the same set of permissions (
chmod g=...). Finally, everyone else (others) gets the same set (
$ ls -l /etc/exim4/passwd.client
-rw-r----- 1 root Debian-exim 204 Oct 15 2006 /etc/exim4/passwd.client
|^^^^^^^^^| |||| ^^^^^^^^^^^
| perms | |||| group
t | owner
t the type of file: blank for plain files,
d for directories,
l for symlinks,
c for character devices,
p for named pipes,
b for block devices, and there are probably a few more I'm forgetting.
acl will be
+ if there is an ACL on this file, you can use
getfacl to see it.
1 I didn't label is the link count; if you made a hard link to the file, both names would show 2. Add another, and they'd show 3, etc.
The permissions field is three characters for the owner (user); three for the group; and three for other. The owner (user) can read and write the file, but not execute (since there is a
- instead of a
x there). Members of the
Debian-exim group can read the file, but get no other permissions. People who are neither the owner nor members of Debian-exim get no permissions to this file.