mpost: 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/mpost - from package: texlive

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

On Debian possible default full paths are:

/usr/bin/mpost - from package: texlive-binaries

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

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