mipsel-linux-gnu-readelf: 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/mipsel-linux-gnu-readelf - from package: binutils-mipsel-linux-gnu

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

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