prefixadmin: 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/prefixadmin - from package: libapp-options-perl

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