myproxy-init: command not found

Have You tried accessing the binary with the full path?

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-init - from package: myproxy

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

On Debian possible default full paths are:

/usr/bin/myproxy-init - from package: myproxy
/usr/lib/debug/usr/bin/myproxy-init - from package: myproxy-dbg

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