Migrate Perl application from Redhat 5 to Redhat 7

Steps involved in migrating Perl application

Chirag S P

2021-11-05

One fine day, I was assigned a project to migrate a perl application( written in the 90s) to Redhat 7 from Redhat 5. Mind you I am a Java developer, but i pride myself in learning anything and everything. So i confidently took in this project as well. Little did I know, the weeks of hell I had to endure to do complete this assignment. So in order to help someone in future below are the steps I followed.

For my use case I am going to setup my Perl application in Redhat 7.9

Install Apache web server

Check if Apache is installed using below command,
```
httpd -v
```
if Apache is present you should get below response,
```
Server version: Apache/2.4.6 (Red Hat Enterprise Linux)
```
If Apache is not present, use below command to install Apache,
```
yum install httpd-devel -y
```
Check if Apache is properly by starting Apache using below command,
```
apachectl start
```
Now in any browser, open the server IP (it maybe ‘localhost’ in your case). In my case I was installing in a new UNIX box having Red hat and I entered the box IP in my browser and tried to open it.
Check if Oracle client is installed by running command
```
env
```
If oracle is installed you’ll have ‘ORACLE_HOME ' present.

If oracle is not installed, download the rpm from oracle site follow the steps to get it installed.

PS: Your DBA should be able provide you the oracle rpm.
After oracle is installed, check if any environment variables are set using below command,
```
env
```
```
 ORACLE_HOME=/app/oracle/product/11.2.0/client_1
```

Make sure ORACLE_HOME , LD_LIBRARY_PATH and PATH are set. If not we can set it manually by editing bash_profile using below command

vi ~/.bash_profile

And add,

export ORACLE_HOME=/app/oracle/product/11.2.0/client_1
export LD_LIBRARY_PATH=$ORACLE_HOME/lib
export PATH=$PATH:$ORACLE_HOME/bin

After oracle client is installed , DB details need to be set.

Create tnsname.ora in oracle client location i.e. at {ORACLE_HOME}/network/admin with below contents,
```
test_s1 =
    (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = test-test.net)(PORT = 1521))
    (CONNECT_DATA =
        (SERVER = DEDICATED)
        (SERVICE_NAME = testSN1)
    )
)
```
Here test_s1 is the system id which you will need pass to your ora_login method in perl script.
Next you need to make sure below environment variables are not set.
```
PERL5LIB="/root/perl5/lib/perl5:"
PERL_LOCAL_LIB_ROOT=":/root/perl5"
PERL_MB_OPT="--install_base /root/perl5"
PERL_MM_OPT="INSTALL_BASE=/root/perl5"
```
If any of the above are present, then unset all of them as shown below,
```
unset PERL5LIB
unset PERL_LOCAL_LIB_ROOT
unset PERL_MB_OPT
unset PERL_MM_OPT
```
This is done so that @INC folder gets installed in user folder instead of root. This is important because Perl expects @INC to be in user folder
Now we install the Perl modules. In my case as I’m using Oracle, so I need to install ‘DBD::Oracle’ module. Also my application contains some legacy Perl4 code. Since Perl4 uses ‘Oraperl’ for DB connections, I need to install ‘Oraperl’ as well.

(We can either uses CPAN or install the modules manually).

CPAN is a package manager for Perl and makes it very easy to install Perl modules,

Perl Module installation. Use either Step A or Step B

A. Using CPAN
```
1.Install CPAN
    yum install perl-CPA
2.Open Cpan shell
    perl -MCPAN -e shell
3.Install DBI
    install Bundle::DBI
4.Install DBD Oracle
    install DBD::Oracle
5.Install Crypt RSA
    install Crypt::RSA
6.Install MIME Base64
    install MIME::Base64
7.Install Oracperl
    install Oraperl
```
B. Without using CPAN

Refer link https://www.perlmonks.org/?node_id=128077
I made sure to give 755 permission for my folder wherein Perl code resides.
Now I had to fix configuration in Apache,

In case of Apache 2.4 configuration files are present at location ‘/etc/httpd/conf/httpd.conf’

Logs are present at ‘/etc/httpd/logs’

There is no htdocs, instead if files needs to picked up by Apache, it needs to placed at location - ‘/var/www/html’. (htdocs is in Apache 2.2 and lower)

To start Apache use below command,
```
apachectl start
```
Next I went to my server IP( in my case the IP was 12**.34.56.789**) and checked if Apache default page was appearing.

Some commonly used Apache commands are as follows,

To stop Apache :
```
apachectl stop
```
To Start Apache:
```
'apachectl start
```
To restart Apache
```
apachectl restart
```
OR
```
systemctl restart httpd
```

Now check if perl modules are installed correctly, by running a sample Perl script and checking if its able to connect DB successfully. Below is the test.pl I used.

#!/opt/perl5/bin/perl

$system_id="test_s1";
$username="testuser";
$password="testuserpass";

print "Content-type: text/html\n\n";
eval 'use Oraperl; 1;' || die $@ if $1] >=5;
$lda = &ora_login($system_id, $username, $password);

if ($ora_errno)
{
    print $ora_errstr;
    print " \n Could not connect to database at $connect_time\n";
}
else{
    print " \n Connected to db at $connect_time\n"
}

Now to create index.html file.

In order for my application to come when I open my server IP location in browser, I had to create index.html at location ‘/var/www/html’

Created ‘index.html’ at location /var/www/html with below contents,
As you can observe, the above path refers to ‘cgi-bin’ folder. This folder needs to be created. After creating this folder, I placed all Perl code in ‘cgi-bin’ file.

At location, ‘/var/www’ I created ‘cgi-bin’ folder.

Inside ‘cgi-bin’ folder I created a link called ‘mycode’(this can anything). This links to my Perl code (or you can place your Perl code directly to location ‘/var/www/cgi-bin’).
Then I gave 755 permission to /var/www and all its sub-directories using below command(path should be /var/www/)
```
chmod -R 775 html
```

Now I had to configure the httpd.conf file.

As mentioned above, this location is /etc/httpd/conf/httpd.conf.

Below are items I had to change/add in httpd.conf

Changed the listen IP and port to the my UNIX box IP andport, as shown below

Listen **12.34.56.789:80**

b. Added below Load Modules

LoadModule authn_file_module modules/mod_authn_file.so
LoadModule authn_dbm_module modules/mod_authn_dbm.so
LoadModule authn_anon_module modules/mod_authn_anon.so
LoadModule authn_dbd_module modules/mod_authn_dbd.so
LoadModule authz_host_module modules/mod_authz_host.so
LoadModule authz_groupfile_module modules/mod_authz_groupfile.so
LoadModule authz_user_module modules/mod_authz_user.so
LoadModule authz_dbm_module modules/mod_authz_dbm.so
LoadModule authz_owner_module modules/mod_authz_owner.so
LoadModule auth_basic_module modules/mod_auth_basic.so
LoadModule auth_digest_module modules/mod_auth_digest.so
LoadModule dbd_module modules/mod_dbd.so
LoadModule dumpio_module modules/mod_dumpio.so
LoadModule reqtimeout_module modules/mod_reqtimeout.so
LoadModule ext_filter_module modules/mod_ext_filter.so
LoadModule include_module modules/mod_include.so
LoadModule filter_module modules/mod_filter.so
LoadModule substitute_module modules/mod_substitute.so
LoadModule deflate_module modules/mod_deflate.so
LoadModule log_config_module modules/mod_log_config.so
LoadModule log_forensic_module modules/mod_log_forensic.so
LoadModule logio_module modules/mod_logio.so
LoadModule env_module modules/mod_env.so
LoadModule mime_magic_module modules/mod_mime_magic.so
LoadModule expires_module modules/mod_expires.so
LoadModule headers_module modules/mod_headers.so
LoadModule usertrack_module modules/mod_usertrack.so
LoadModule unique_id_module modules/mod_unique_id.so
LoadModule setenvif_module modules/mod_setenvif.so
LoadModule version_module modules/mod_version.so
LoadModule mime_module modules/mod_mime.so
LoadModule dav_module modules/mod_dav.so
LoadModule status_module modules/mod_status.so
LoadModule autoindex_module modules/mod_autoindex.so
LoadModule asis_module modules/mod_asis.so
LoadModule info_module modules/mod_info.so
LoadModule cgi_module modules/mod_cgi.so
LoadModule cgid_module modules/mod_cgid.so
LoadModule dav_fs_module modules/mod_dav_fs.so
LoadModule vhost_alias_module modules/mod_vhost_alias.so
LoadModule negotiation_module modules/mod_negotiation.so
LoadModule dir_module modules/mod_dir.so
LoadModule actions_module modules/mod_actions.so
LoadModule speling_module modules/mod_speling.so
LoadModule userdir_module modules/mod_userdir.so
LoadModule alias_module modules/mod_alias.so
LoadModule rewrite_module modules/mod_rewrite.so

c. Created a new user and group in my Unix server and set the same as below.

User exampleUser
Group exampleGroup

d. Changed ‘Directory’ tag to as shown below.

<Directory />
    Options FollowSymLinks
    AllowOverride None
    Order deny,allow
    Deny from all
</Directory>

c. Changed ‘Directory “/var/www”’ as below.

<Directory "/var/www">
</Directory>

d. Changed ‘Directory “/var/www/html”’ as below

<Directory "/var/www/html">
    #
    # Possible values for the Options directive are "None", "All",
    # or any combination of:
    #   Indexes Includes FollowSymLinks SymLinksifOwnerMatch ExecCGI MultiViews
    #
    # Note that "MultiViews" must be named *explicitly* --- "Options All"
    # doesn't give it to you.
    #
    # The Options directive is both complicated and important.  Please see
    # http://httpd.apache.org/docs/2.4/mod/core.html#options
    # for more information.
    #
    Options Indexes FollowSymLinks ExecCGI

    #
    # AllowOverride controls what directives may be placed in .htaccess files.
    # It can be "All", "None", or any combination of the keywords:
    #   Options FileInfo AuthConfig Limit
    #
    AllowOverride None

    #
    # Controls who can get stuff from this server.
    #
    Order allow,deny
    Allow from all
</Directory>

e. Changed ‘IfModule alias_module tag as below. Here I had to declare the different ‘ScriptAlias’ present in my Perl scripts.

<IfModule alias_module>
    #
    # Redirect: Allows you to tell clients about documents that used to
    # exist in your server's namespace, but do not anymore. The client
    # will make a new request for the document at its new location.
    # Example:
    # Redirect permanent /foo http://www.example.com/bar

    #
    # Alias: Maps web paths into filesystem paths and is used to
    # access content that does not live under the DocumentRoot.
    # Example:
    # Alias /webpath /full/filesystem/path
    #
    # If you include a trailing / on /webpath then the server will
    # require it to be present in the URL.  You will also likely
    # need to provide a <Directory> section to allow access to
    # the filesystem path.

    #
    # ScriptAlias: This controls which directories contain server scripts.
    # ScriptAliases are essentially the same as Aliases, except that
    # documents in the target directory are treated as applications and
    # run by the server when requested rather than as documents sent to the
    # client.  The same rules about trailing "/" apply to ScriptAlias
    # directives as to Alias.
    #
    ScriptAlias /cgi-bin/ "/var/www/cgi-bin/"
    ScriptAlias /images/ "/var/www/cgi-bin/content/images/"
        ScriptAlias /log/ "/var/www/cgi-bin/content/login/"
    ScriptAlias /bin/logoff "/var/www/cgi-bin/content/html/logoff.html"

</IfModule>

f. Changed ‘Directory “/var/www/cgi-bin”’ to below

<Directory "/var/www/cgi-bin">
    AllowOverride None
    Options Indexes FollowSymLinks ExecCGI
    Order allow,deny
    Allow from all
    AddHandler cgi-script .pl .class .new
</Directory>

g. Changed ‘IfModule mime_module’ tag to below,

<IfModule mime_module>
    #
    # TypesConfig points to the file containing the list of mappings from
    # filename extension to MIME-type.
    #
    TypesConfig /etc/mime.types

    #
    # AddType allows you to add to or override the MIME configuration
    # file specified in TypesConfig for specific file types.
    #
    #AddType application/x-gzip .tgz
    #
    # AddEncoding allows you to have certain browsers uncompress
    # information on the fly. Note: Not all browsers support this.
    #
    #AddEncoding x-compress .Z
    #AddEncoding x-gzip .gz .tgz
    #
    # If the AddEncoding directives above are commented-out, then you
    # probably should define those extensions to indicate media types:
    #
    AddType application/x-compress .Z
    AddType application/x-gzip .gz .tgz

    #
    # AddHandler allows you to map certain file extensions to "handlers":
    # actions unrelated to filetype. These can be either built into the server
    # or added with the Action directive (see below)
    #
    # To use CGI scripts outside of ScriptAliased directories:
    # (You will also need to add "ExecCGI" to the "Options" directive.)
    #
    #AddHandler cgi-script .cgi
    AddHandler cgi-script .class
    AddHandler cgi-script .cgi .pl .class .jsp
    AddHandler default-handler .jpg .png .css .ico .gif .html .log

    # For type maps (negotiated resources):
    #AddHandler type-map var

    #
    # Filters allow you to process content before it is sent to the client.
    #
    # To parse .shtml files for server-side includes (SSI):
    # (You will also need to add "Includes" to the "Options" directive.)
    #
    #AddType text/html .shtml
    #AddOutputFilter INCLUDES .shtml
</IfModule>

h. Also added below oracle paths as well in httpd.conf dile.

SetEnv LD_LIBRARY_PATH /app/oracle/product/11.2.0/client_1/lib
SetEnv ORACLE_HOME /app/oracle/product/11.2.0/client_1

Also I made add below code in all my .pl file which contain print statements.
```
print "Content-type: text/html\n\n";
```
(or else it will cause Apache to download .pl file instead of executing it. Make sure to check files of any inner subroutines as well. Above code should be present.)