ghostscript: 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/ghostscript - from package: ghostscript

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

On Debian possible default full paths are:

/usr/bin/ghostscript - from package: ghostscript

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

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