gnome-disks: 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/bin/gnome-disks - from package: gnome-disk-utility

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

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