backup-manager-purge: 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 CentOS possible default full paths are:

/usr/bin/backup-manager-purge - from package: backup-manager

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/backup-manager-purge - from package: backup-manager

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

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