Apache Custom Header with an environment variable

Question

I try to set a custom HTTP Header with an environment variable** with Apache server 2.4.6 and headers_module.

I work inside a HTTP VHost on port 80.

Everything work as expected with basic example like:

Header set MyHeader "%D %t"

I have read the Apache Documentation of mod_headers : https://httpd.apache.org/docs/2.4/en/mod/mod_headers.html#header

It is said that one can access environment variable using %{ENVVARNAME}e

(with ENVVARNAME the name of the ENV variable)

I also read other post but no real working answer: Apache set custom header with an evironment variable

But my problem is to add a header than identify my Apache Server like the HOSTNAME environment value

1. I tried this

Header Set X-Serv %{HOSTNAME}e

No success : always display X-Serv:{null} instead of the value

2. I also tried :

SetEnv myvar ${HOSTNAME} Header set X-Serv %{myvar}e

No success : it displays in my HTTP Headers : X-Serv: %{myvar}e

I also tried some other various combinations:

Please note: My HOSTNAME environment variable exists and it display in 'env' command with the apache user owning the httpd process

Any idea?

Answer 1

You have to declare which system environment variables you want to be usable with the PassEnv directive

A working example would be:

PassEnv HOSTNAME
Header Set X-Serv %{HOSTNAME}e

Answer 2

Found a way to get it working:

• Ensure module is activated (mod_headers) or activate if necessary

  a2enmod headers
  

• in /etc/apache2/envvars add

  export HOSTNAME=`uname -n`
  

• in <VirtualHost> clause

  Header set apachehost ${HOSTNAME}
  

• Restart or reload httpd service

  service apache2 restart
  

Answer 3

1.Ensure module is activated (mod_headers) or activate if necessary

a2enmod headers

2.in /etc/apache2/envvars add

export HOSTNAME1=`uname -n` or `hostname`

3.in <VirtualHost _default:443> clause

PassEnv HOSTNAME1

Header set X-Server "%{HOSTNAME1}e"

4.Restart or reload httpd service

service apache2 restart