clog2_join: 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/clog2_join - from package: mpich2

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

Error in other languages:
clog2_join: bevel nie gevind nie
clog2_join: comandă negăsită
clog2_join: comando não encontrado
clog2_join: commande introuvable
clog2_join: command not found
clog2_join: käsku ei ole
clog2_join: không tìm thấy lệnh
clog2_join: komanda nerasta
clog2_join: Kommando nicht gefunden.
clog2_join: kommandot finns inte
clog2_join: komut yok
clog2_join: nie znaleziono polecenia
clog2_join: níor aimsíodh an t-ordú
clog2_join: no se encontró la orden
clog2_join: no s'ha trobat l'ordre
clog2_join: opdracht niet gevonden
clog2_join: parancs nem található
clog2_join: perintah tidak ditemukan
clog2_join: príkaz nenájdený
clog2_join: příkaz nenalezen
clog2_join: команда не найдена
clog2_join: командата не е открита
clog2_join: 命令找不到
clog2_join: コマンドが見つかりません