dm-tool: 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/dm-tool - from package: lightdm

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

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