ipcevents: 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/ipcevents - from package: xsupplicant

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

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