ovsdb-client: 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/ovsdb-client - from package: openvswitch-common

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

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