response 1 of 15:

Feb 24 16:02 UTC 2006

chmod +x filename  - makes a file executable by anyone.  You can probably find
lots of information about chmod on the web with a search engine, in simpler
language than the manual (man) pages.  (or does +x make is executable only
by root?  I am always root).

response 3 of 15:

Feb 24 17:12 UTC 2006

This would be better in the Unix conference, but....

chmod +x makes a file executable by anyway.

Unix file permissions work like this: There are three separate permission
bits: Read, Write, and Execute.  These are replicated for three separate
classes of users: The user who owns the file, the *group* that `owns' the
file, and everybody else.

The chmod bit changese these permission bits.  (There are a few others,
but we needn't go into them right now).  You may either specify permissions
symbolically, or in octal.  In the latter, you use numbers to specify what
the permissions should be.  You usually give a three digit number that
specifies read, write, and execute for user, group, and world all at once.
04 is read, 02 is write, and 01 is execute.  You add these together to
get what permissions you want.  So, 04 + 02 = 06 is read and write.
04 + 02 + 01 = 07 is read, write, and execute.  04 + 01 = 05 is read and
execute.  You then give three digits, so 755 is read, write, and execute
for user, and read and execute for both group and other.  To apply these
to a file, you would type, e.g., `chmod 755 file'.

In the symbolic system, permission bits are represented by letters,
`r' for read, `w' for write, and `x' for execute.  You use `+' or
`-' to set.  E.g., `chmod +x file' adds execute permissions for
everybody while, `chmod -x file' removes them.  Similarly for
`chmod +r file', `chmod -r file', `chmod +w file' and `chmod -w file'.
You can combine these in an obvious way to set multiple bits at once.
E.g, `chmod +rx file' to make the file readable and executable at once.
Note that in the octal system, all permissions are set at once.  In
the symbolic system, you modify permissions.  So, if a file is writable,
doing `chmod +x file' doesn't make it *unwritable* whereas,
`chmod 111 file' does.  Octal sets permissions absolutely, symbolic
modifies them.

You can also change permissions for group or owner individually in
the symbolic system.  For instance, `chmod u+w file' makes the file
writable by the user, but doesn't affect anything else.  `chmod go-w file'
makes it *unwritable* by group and other (note that `o' stands for `other'
not `owner,' and similarly, `u' is for `user').

There's also the `=' system of doing things, which sets bits absolutely in
the symbolic system, but this should be enough to get you started.

response 5 of 15:

Feb 24 18:34 UTC 2006

I'm not on my Linux system now, but I believe it's chattr +i (for "immutable").
(Finding some such files that you didn't put there is a nearly-sure sign that
you've been hacked.)

response 7 of 15:

Feb 24 20:33 UTC 2006

Can you make an entire directory non-erasable?

response 9 of 15:

Feb 25 04:53 UTC 2006

Check the man page for the `chflags' command.

response 11 of 15:

Feb 25 13:38 UTC 2006

Re #9:  Ah, thanks.  I seemed to recall that OpenBSD had some sort of
extended file attribute support but didn't remember how to access it. 
In particular, "chflags uchg FILE" makes FILE "immutable", which seems
to mean undeletable and uneditable (even if the file and its directory
have write permission set).  "ls -lo" lists the extended attributes.

response 13 of 15:

Feb 26 06:25 UTC 2006

unlucky

response 15 of 15:

May 17 02:16 UTC 2006

TROGG IS DAVID BLAINE