update-locale: 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/update-locale - from package: gosa-dev
/usr/sbin/update-locale - from package: locales

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

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