a2x: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/a2x - from package: asciidoc

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/a2x - from package: asciidoc

You may install the required package with command apt-get install {package}

Error in other languages:
a2x: bevel nie gevind nie
a2x: comandă negăsită
a2x: comando não encontrado
a2x: commande introuvable
a2x: command not found
a2x: käsku ei ole
a2x: không tìm thấy lệnh
a2x: komanda nerasta
a2x: Kommando nicht gefunden.
a2x: kommandot finns inte
a2x: komut yok
a2x: nie znaleziono polecenia
a2x: níor aimsíodh an t-ordú
a2x: no se encontró la orden
a2x: no s'ha trobat l'ordre
a2x: opdracht niet gevonden
a2x: parancs nem található
a2x: perintah tidak ditemukan
a2x: príkaz nenájdený
a2x: příkaz nenalezen
a2x: команда не найдена
a2x: командата не е открита
a2x: 命令找不到
a2x: コマンドが見つかりません