knfs: 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/knfs - from package: openafs-client

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

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