ovsdb-tool: 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/lib/debug/usr/bin/ovsdb-tool - from package: openvswitch-dbg
/usr/bin/ovsdb-tool - from package: openvswitch-switch

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