taskcoach: 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/taskcoach - from package: taskcoach

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

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