kcheckrunning: 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/kcheckrunning - from package: kdebase-workspace

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

On Debian possible default full paths are:

/usr/bin/kcheckrunning - from package: kde-workspace-bin

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

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