isfile: 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/isfile - from package: wcstools

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

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