qextract: 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 Debian possible default full paths are:

/usr/bin/qextract - from package: qfits-tools

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

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