SERVER_A: 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/debian-lan-config/fai/config/files/usr/local/sbin/debian-lan/SERVER_A - from package: debian-lan-config
/usr/share/debian-lan-config/fai/config/files/usr/local/sbin/dhcpd-keytab/SERVER_A - from package: debian-lan-config

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

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