dphys-swapfile: 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:

/sbin/dphys-swapfile - from package: dphys-swapfile

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

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