wireshark-qt: 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/wireshark-qt - from package: wireshark-qt

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

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