texliveonfly: 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/texliveonfly - from package: texlive-extra-utils

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

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