delta-filter: 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/delta-filter - from package: mummer

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

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