arcstat: 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/arcstat - from package: nordugrid-arc-client

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

On Debian possible default full paths are:

/usr/bin/arcstat - from package: nordugrid-arc-client

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

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