Patch with the supplied file (openssh-3.5p1.diff) [see Listing 1] or change configure.ac by hand following the previous hints:

devsys# cd openssh-3.5p1
devsys# patch -Np0 -i ../openssh-3.5p1.diff

Now, run autoconf to generate the configure script. If autoconf complains it does not find configure.in, upgrade your version. (This is the case with Red Hat 7.2). Get the newer version from ftp.gnu.org/pub/gnu/autoconf/autoconf-2.57.tar.gz then compile and install it.

devsys# autoconf

devsys# ./configure --host=arm-linux --target=arm-linux 
> --build=i686-linux --libexecdir=/bin --sysconfdir=/etc/ssh 
> --disable-lastlog --disable-utmp --disable-largefile 
> --disable-utmpx --disable-wtmp --disable-wtmpx --without-pam 
> --without-4in6 --with-pid-dir=/var/run --with-ipv4-default

devsys# make
devsys# cp ssh scp ssh-keygen sshd sshd_config ssh_config $BINS_DIR

Uploading the Applications

In the first step we strip all binaries of unneeded symbols:

devsys# cd $BINS_DIR
devsys# arm-linux-strip --strip-all *

Don't worry that some text formats will not be recognized; the binaries are stripped anyway.

Transferring Files from the Development System to the CerfCube

Having a password-less ssh (and scp) connection to the CerfCube is advantageous. Otherwise, the password is requested before every scp transfer. When we compile Perl, this could mean typing the same password more than 30 times.

To achieve a password-less ssh connection to the CerfCube, type devsys# cd ~/.ssh. Then, check to see if you have the file id_dsa.pub in this directory. If not, generate it with devsys# ssh-keygen -t dsa -P “”. Accept the default directory offered by pressing Enter, and copy this key to your CerfCube:

CerfCube# mkdir -p /root/.ssh
CerfCube# cd /root/.ssh

Send your id_dsa.pub key from your development system. You should be asked for the root password in the CerfCube. I am assuming an address 192.168.2.7; change it to suit your configuration.

devsys# scp id_dsa.pub [email protected]:/root/.ssh

In the CerfCube, append the id_dsa.pub key to the authorized keys file:

CerfCube# cat id_dsa.pub >> authorized_keys2

Now, we can start transferring files with devsys# cd $BINS_DIR. We have to change the name of scp to transfer it, though. The running instance of scp does not let itself be replaced by another binary with the same name and complains about being busy. The same is valid for sshd.

devsys# mv scp scpnew
devsys# mv sshd sshdnew
devsys# scp libcrypto.so.0.9.7 libssl.so.0.9.7 
> libz.so.1.1.4 [email protected]:/usr/lib
devsys# scp gdb boa ssh ssh-keygen scpnew [email protected]:/usr/bin
devsys# scp sshdnew inetd proftpd
devsys# scp proftpd.conf [email protected]:/etc
devsys# scp ssh*_config [email protected]:/etc/ssh
devsys# scp boa.conf [email protected]:/etc/boa

We register the new libraries in the CerfCube with CerfCube# ldconfig -v. Observe that libz appears as modified; actually, it was upgraded to the latest version.

In the CerfCube we activate sshd and scp but leave the old versions just in case:

CerfCube# cd /usr/bin
CerfCube# mv scp scpold
CerfCube# mv scpnew scp
CerfCube# cd /usr/sbin
CerfCube# mv sshd sshdold
CerfCube# mv sshdnew sshd

Compiling Perl

Perl 5.8 has a feature that tests made at configure time are run remotely in the CerfBoard. This implies, of course, the necessity of working ssh tools on both the CerfCube and the development system. For added comfort, a password-less ssh connection, as set before, is advantageous.

devsys# export PFIX=/usr/local/arm/2.95.3/arm-linux
devsys# cd $SRC_DIR
devsys# wget http://www.cpan.org/src/5.0/stable.tar.gz
devsys# tar zxf stable.tar.gz
devsys# cd perl-5.8.0
devsys# ./Configure -des -Dusecrosscompile -Dtargethost=192.168.2.7 
> -Dtargetdir=/tmp -Dtargetuser=root -Dtargetarch=arm-linux 
> -Dcc=arm-linux-gcc -Dusrinc=$PFIX/include -Dincpth=$PFIX/include 
> -Dlibpth=$PFIX/lib
devsys# make

Configuration is done with sensible default values, thanks to the -des options. Remember to put the arm-linux utilities in your search path. At the end of the compilation, you should end up with an executable named miniperl–not so mini, considering it is about 1MB after stripping. As with some other cross compilation aware applications, this one tries to run cross compiled binaries in the wrong environment, generating some error messages. But, Perl is compiled. Upload to your board and enjoy.

devsys# scp miniperl [email protected]:/usr/bin/perl

Postconfiguration of the CerfCube

To reflect the configuration of the FTP server, do the following on the CerfCube:

1. Add the following line to /etc/inetd.conf:

   
   CerfCube# echo "ftp stream tcp nowait root /usr/sbin/proftpd proftpd"
   >> /etc/inetd.conf

2. Add the user ftp and create the directory from which files will be served (/home/ftp):

   
   CerfCube# echo "ftp:*:100:100::/home/ftp:/bin/false" >> /etc/passwd
   CerfCube# mkdir /home/ftp
   

3. Add the group nogroup, with the ID number 100, as set in the previous line:

   
   CerfCube# echo "nogroup:*:100:" >> /etc/group
   

Use the following steps to configure the ssh tools:

1. Generate keys for the ssh utilities in the /etc/ssh directory (the sysconfdir at configure time):

   
   CerfCube# ssh-keygen -t dsa -f /etc/ssh/ssh_host_dsa_key -P ""
   CerfCube# ssh-keygen -t rsa1 -f /etc/ssh/ssh_host_rsa_key -P ""
   CerfCube# ssh-keygen -t rsa -f /etc/ssh/ssh_host_key -P ""
   

2. Create the sshd user:

   
   CerfCube# echo "sshd:*:101:100::/var/run/sshd:/bin/false" >> /etc/passwd

3. Edit /etc/ssh/sshd_config to contain the line UsePrivilegeSeparation no and uncomment it. If you want to have a privilege separation directory, it must be /var/empty, which is erased every time you turn off the CerfCube. Be sure to have it created in the startup scripts before sshd is started. Otherwise, sshd won't start.

These are the steps necessary to configure the web server:

1. Create the directory where the server should keep its documents. Remember, we previously created the directory /etc/boa, and the configuration file boa.conf is in that directory.

   
   CerfCube# mkdir -p /home/httpd/cgi-bin
   

2. To run the web server, /etc/boa/boa.conf needs to be edited in at least the following directives:

   
   ErrorLog: set it to /dev/null to avoid error logging
   AccessLog: comment out to avoid access logging
   MimeTypes: set to /dev/null if you don't have a mime.types file
   DocumentRoot: set it to the directory from which you will be serving
    your html documents (/home/http)
   ScriptAlias: set the second part to the directory in which your
    CGIs will reside, (/home/httpd/cgi-bin in this case).

Configuring Perl for CGI

The CGI module is standard in the latest Perl distributions, but our Perl installation in the CerfCube does not include any libraries. The CGI module depends on other modules. Generating those modules in the CerfCube requires a working C compiler that, of course, does not fit in the CerfCube. The solution is to copy the necessary modules from the Perl installation on your development system. Perl 5.6 and 5.8 modules work fine; other Perl versions were not tested.

Using the configuration values given when compiling Perl, modules are expected to reside in a directory under /usr/local/lib/perl5. This could be the directory 5.8.0. Create that directory first:

CerfCube# mkdir -p /usr/local/lib/perl5/5.8.0/{CGI,warnings}

If your development system has Perl 5.6, simply issue the following command from there:

devsys# cd /usr/lib/perl5/5.6.0
devsys# scp CGI.pm overload.pm shellwords.pl [email protected]:/usr/local/lib/perl5/5.8.0

If your development system has Perl 5.8, you need some more files:

devsys# cd /usr/lib/perl5/5.8.0
devsys# scp CGI.pm overload.pm Carp.pm Exporter.pm strict.pm vars.pm 
> warnings.pm constant.pm overload.pm [email protected]:/usr/local/lib/perl5/5.8.0
devsys# scp CGI/Util.pm [email protected]:/usr/local/lib/perl5/5.8.0/CGI
devsys# scp warnings/register.pm [email protected]:/usr/local/lib/perl5/5.8.0/warnings

Testing the Servers

You can start your Boa HTTP server either manually or with a startup script. To test the server, create an index.html file in /home/httpd. Now, point a browser to http://192.168.2.7/index.html. You should see the page you created. If you type http://192.168.2.7/, the index.html file is interpreted as a directory listing, and the HTML contents are displayed as plain text in the browser.

To test your CGI environment, use the following script (found in stein.cshl.org/WWW/CGI, as an example to the Perl module CGI.pm). Name it test.cgi and place it in /home/httpd/cgi-bin.

#!/usr/bin/perl

use CGI qw(:standard);

print header;
print start_html('A Simple Example'),
    h1('A Simple Example'),
    start_form,
    "What's your name? ",textfield('name'),
    p,
    "What's the combination?",
    p,
    checkbox_group(-name=>'words',
                   -values=>['eenie','meenie','minie','moe'],
                   -defaults=>['eenie','minie']),
    p,
    "What's your favorite color? ",
    popup_menu(-name=>'color',
               -values=>['red','green','blue','chartreuse']),
    p,
    submit,
    end_form,
    hr;

   if (param()) {
    print
        "Your name is",em(param('name')),
        p,
        "The keywords are: ",em(join(", ",param('words'))),
        p,
        "Your favorite color is ",em(param('color')),
        hr;
   }
   print end_html;

Make it executable (chmod 700), and invoke it from a browser with the URL http://192.168.2.7/cgi-bin/test.cgi. It should display a form. When you press Submit Query, you should see the data you entered at the bottom.

To use the FTP server, it is necessary to first run inetd. You can run it manually or from a startup script with CerfCube# inetd. Now, you can copy any file to /home/ftp/ and from your development system connect to your FTP server with devsys# ftp 192.168.2.7. Now you have a working FTP server.

About the Author: Ricardo Restrepo has been working with Linux for seven years and with embedded systems under Linux for one year. He enjoys learning living and extinct human and computer languages, reading classics in their original languages when possible, listening to Bach and jogging.

Copyright © 2003 Specialized Systems Consultants, Inc., publishers of the monthly magazine Linux Journal. All rights reserved. Embedded Linux Journal Online is a cooperative project of Linux Journal and LinuxDevices.com.

 
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