xml2ads: 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/xml2ads - from package: bibutils

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

On Debian possible default full paths are:

/usr/bin/xml2ads - from package: bibutils

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

Error in other languages:
xml2ads: bevel nie gevind nie
xml2ads: comandă negăsită
xml2ads: comando não encontrado
xml2ads: commande introuvable
xml2ads: command not found
xml2ads: käsku ei ole
xml2ads: không tìm thấy lệnh
xml2ads: komanda nerasta
xml2ads: Kommando nicht gefunden.
xml2ads: kommandot finns inte
xml2ads: komut yok
xml2ads: nie znaleziono polecenia
xml2ads: níor aimsíodh an t-ordú
xml2ads: no se encontró la orden
xml2ads: no s'ha trobat l'ordre
xml2ads: opdracht niet gevonden
xml2ads: parancs nem található
xml2ads: perintah tidak ditemukan
xml2ads: príkaz nenájdený
xml2ads: příkaz nenalezen
xml2ads: команда не найдена
xml2ads: командата не е открита
xml2ads: 命令找不到
xml2ads: コマンドが見つかりません