thepeg: 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/thepeg - from package: thepeg-gui

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

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