hgtk: 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/hgtk - from package: tortoisehg

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

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