gm-backup_database: 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/sbin/gm-backup_database - from package: gnumed-server

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

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