mizuho: 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 CentOS possible default full paths are:

/usr/bin/mizuho - from package: rubygem-mizuho
/usr/lib/ruby/gems/1.8/gems/mizuho-0.9.20/bin/mizuho - from package: rubygem-mizuho

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/mizuho - from package: ruby-mizuho

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

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