hp2ps: 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/hp2ps - from package: ghc-compiler

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

On Debian possible default full paths are:

/usr/bin/hp2ps - from package: ghc
/usr/lib/ghc/bin/hp2ps - from package: ghc

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

Error in other languages:
hp2ps: bevel nie gevind nie
hp2ps: comandă negăsită
hp2ps: comando não encontrado
hp2ps: commande introuvable
hp2ps: command not found
hp2ps: käsku ei ole
hp2ps: không tìm thấy lệnh
hp2ps: komanda nerasta
hp2ps: Kommando nicht gefunden.
hp2ps: kommandot finns inte
hp2ps: komut yok
hp2ps: nie znaleziono polecenia
hp2ps: níor aimsíodh an t-ordú
hp2ps: no se encontró la orden
hp2ps: no s'ha trobat l'ordre
hp2ps: opdracht niet gevonden
hp2ps: parancs nem található
hp2ps: perintah tidak ditemukan
hp2ps: príkaz nenájdený
hp2ps: příkaz nenalezen
hp2ps: команда не найдена
hp2ps: командата не е открита
hp2ps: 命令找不到
hp2ps: コマンドが見つかりません