debconf-get-selections: command not found

Have You tried accessing the binary with the full path?

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/debconf-get-selections - from package: debconf-utils

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