abootimg-unpack-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/bin/abootimg-unpack-initrd - from package: abootimg

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

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