a-rex-backtrace-collect: 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/a-rex-backtrace-collect - from package: nordugrid-arc-arex

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

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