pvserver_mpich: 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/lib64/mpich/bin/pvserver_mpich - from package: paraview-mpich

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

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