qconvex: 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/qconvex - from package: qhull

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

On Debian possible default full paths are:

/usr/bin/qconvex - from package: qhull-bin

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

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