myproxy-change-pass-phrase: 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/myproxy-change-pass-phrase - from package: myproxy

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

On Debian possible default full paths are:

/usr/bin/myproxy-change-pass-phrase - from package: myproxy

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

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