pekwm: 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/pekwm - from package: pekwm

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

On Debian possible default full paths are:

/usr/bin/pekwm - from package: pekwm

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

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