LinuxHostingSupport

Your perl script sometimes work from the command line but shows “Internal Server Error” on accessing the script via the browser. The Apache error logs shows the error message as

"Can't do setuid (cannot exec sperl)".

The the reason for the setuid error on the  perl script is the script have the setuid bit set and won’t work from the browser since they are running under the user apache. To make such perl scripts work, you need to install the perl-suidperl package.

To install the package, just execute the command

# yum install perl-suidperl

You may see quite a few maildrop warning messages in the postfix logs such as

postdrop: warning: mail_queue_enter: create file maildrop/xxxx.xxxx: Permission denied
postdrop: warning: mail_queue_enter: create file maildrop/yyyy.yyyy: Permission denied

The error occurs when postfix is not able to write under the “maildrop” folder and hence unable to send emails. This is due to incorrect ownership on the ‘maildrop’ folder i.e. the “maildrop” folder is not owned by ‘postfix’.

Check the ownership/permissions of the postfix files:

# /etc/init.d/postfix check
postfix/postfix-script: warning: not owned by postfix: /var/spool/postfix/public
postfix/postfix-script: warning: not owned by postfix: /var/spool/postfix/maildrop

Solution:

Stop the postfix service:

# /etc/init.d/postfix stop

Kill the postdrop processes:

# killall -9 postdrop

Correct the ownership of the above directories:

# chown postfix.postdrop /var/spool/postfix/public -R
# chown postfix.postdrop /var/spool/postfix/maildrop -R

Now, start the postfix service:

# /etc/init.d/postfix start

Emails should now be working fine.

How to redirect a website using .htaccess?

Redirect website http://mydomain.com to http://www.mynewdomain.com

RewriteEngine on
RewriteCond %{HTTP_HOST} ^mydomain\.com$
RewriteRule ^(.*)$ http://www.mynewdomain.com [R=301,L]

Redirect website mydomain.com with and without www requests to http://www.mynewdomain.com

RewriteEngine on
RewriteCond %{HTTP_HOST} ^www\.mydomain\.com$ [OR]
RewriteCond %{HTTP_HOST} ^mydomain\.com$
RewriteRule ^(.*)$ http://www.mynewdomain.com [R=301,L]

Redirect requests from http://mydomain.com to http://mydomain.com/subdirectory i.e. redirecting requests from main domain to a sub-directory.

RewriteEngine on
RewriteCond %{HTTP_HOST} ^www\.mydomain\.com$ [OR]
RewriteCond %{HTTP_HOST} ^mydomain\.com$
RewriteRule ^(.*)$ http://www.mydomain.com/subdirectory/ [R=301,L]

Redirect all http (80) requests of a domain to https (443) i.e. redirecting requests from non-secure port to a secure port.

RewriteEngine On
RewriteCond %{SERVER_PORT}      !443
RewriteRule ^(.*)$ https://mydomain.com/$1 [R,L]

You may see the tty device error messages like ‘/dev/tty1: cannot open as standard input: Permission denied’ in the server logs and many more like

Jan 10 xx:xx:xx [agetty] /dev/tty1: cannot open as standard input: Permission denied
Jan 10 xx:xx:xx [agetty] /dev/tty2: cannot open as standard input: Permission denied
Jan 10 xx:xx:xx [agetty] /dev/tty3: cannot open as standard input: Permission denied
Jan 10 xx:xx:xx [init] Id “c1” respawning too fast: disabled for 5 minutes
Jan 10 xx:xx:xx [init] Id “c2” respawning too fast: disabled for 5 minutes
Jan 10 xx:xx:xx [init] Id “c3” respawning too fast: disabled for 5 minutes

The tty “Permission denied” error message is because of the misconfiguration in your /etc/inittab file in which case you have to edit the file and comment the agetty/getty lines. Login to your server as root and edit the file:

pico /etc/inittab

Search for the lines

c1:12345:respawn:/sbin/agetty 38400 tty1 linux

and comment the lines by placing a # in front of them.

Save the file and you won’t see the messages.

OR

you may try re-creating the terminals again from shell as root. Login to your server as root and execute the command:

/sbin/makedev /dev/tty1

and replace 1 with 2,3,4,5,6,7 for other terminals and reboot the server.

What is .htaccess and how to disable .htaccess?

.htaccess is use to modify the way Apache behaves for a directory and it’s sub-directories. It gives you an extra control on your server, like setting up custom error messages, password protect a directory, writing rewrite rules, blocking IPs etc.

However, it can be a potentially dangerous file. For example, a hacker can redirect your website to an external website say a malware website.

In order to disable .htaccess server wide, edit the Apache configuration file

pico /etc/httpd/conf/httpd.conf

Search for

AllowOverride All

replace it with

AllowOverride None

Save the file and restart the Apache service.

service httpd restart