insert a line or a file to /etc

j-me · 07-23-2009, 12:42 PM

I am trying to create a script to add a line to the /etc/exports file. I am root user and can do it from cli but when I put an echo 'test' >> /etc/testfile or echo 'add line' >> /etc/exports in a script I get a 'permission denied'. What do I need to do to make this work within a script?

Thank you.

bsdunix · 07-23-2009, 12:59 PM

Is the executable bit set on the script?

http://unixhelp.ed.ac.uk/scrpt/scrpt1.2.html

j-me · 07-23-2009, 01:02 PM

Yes. the script does execute. I tested it by just doing an echo 'hello' and that executed fine. Thanks.

repo · 07-23-2009, 01:03 PM

Quote:

I get a 'permission denied

Where do you get the permission denied?
Can you post the error messages ?

PTrenholme · 07-23-2009, 01:10 PM

Code:

Peter@dv9710us:~ $ sudo touch /etc/testfile
[sudo] password for Peter:                 
Peter@dv9710us:~ $ sudo echo Test > /etc/testfile
bash: /etc/testfile: Permission denied           
Peter@dv9710us:~ $ ls -l /etc/testfile           
-rw-r--r--. 1 root root 0 2009-07-23 10:50 /etc/testfile

<edit>
Note that, whilst the SELinux context is set (the . in -rw-r--r--.), I have SELinux set to "permissive" mode, so that shouldn't be a problem.
</edit>

<edit2>
On the other hand . . .

Code:

Peter@dv9710us:~ $ su -
Password:              
[root@dv9710us ~]# echo Test > /etc/testfile 
[root@dv9710us ~]# ls -l /etc/testfile*
-rw-r--r--. 1 root root 5 2009-07-23 11:18 /etc/testfile
[root@dv9710us ~]# cat /etc/testfile                    
Test

</edit2>

Tinkster · 07-23-2009, 01:17 PM

j-me and PTrenholme the same person? :}

Anyway: the problem is that you echo as root, but the redirect happens
to the sudo-part.

What you need to do is:

Code:

sudo sh -c "echo hello > /etc/testfile"

j-me · 07-23-2009, 01:19 PM

Here is what I get:

cp: cannot create regular file `/etc/exports-j-me': Permission denied

script:
cp /etc/exports .
echo 'testing' >> exports
cp -f exports /etc/exports-j-me

I execute from a working directory.
make a copy of the exports file
insert a line at bottom of the file.
copy the changed file back over.
the first two steps work. the last step is where I receive an error.

j-me · 07-23-2009, 01:28 PM

i'll be damned, it works! That you oh wise one!

Thanks to all for their quick response.

j-me · 07-23-2009, 01:34 PM

can you explain what the "sudo sh -c does? execute within a shell? I remember reading something about this.
Thanks.

Tinkster · 07-23-2009, 01:47 PM

I'm far from wise, I'm afraid ... but I can read, and
occasionally understand what I take in ;}

After a decade or so of Linux use it seemed "obvious" that the
re-direct was not part of what's run under sudo (otherwise a
permission problem wouldn't have arisen). How to wrap that all
up would have taken me a few minutes of thought, instead I looked
at the sudo man-page and searched for re-direct.

From the sudo man-page

Code:

       To make a usage listing of the directories in the /home partition.
       Note that this runs the commands in a sub-shell to make the cd and file
       redirection work.

        $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE"

Cheers,
Tink