select-boot-kernel-initrd: 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/share/diskimage-builder/elements/select-boot-kernel-initrd/bin/select-boot-kernel-initrd - from package: python-diskimage-builder

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

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