pt-online-schema-change: 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/pt-online-schema-change - from package: percona-toolkit

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

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