dpkg: 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/dpkg - from package: dpkg

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

On Debian possible default full paths are:

/usr/bin/dpkg - from package: dpkg

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

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