tasksel: 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/tasksel - from package: tasksel

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

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