myproxy-server: 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/sbin/myproxy-server - from package: myproxy-server

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

On Debian possible default full paths are:

/usr/sbin/myproxy-server - from package: myproxy-server
/usr/lib/debug/usr/sbin/myproxy-server - from package: myproxy-dbg

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

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