ksysguard: 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/ksysguard - from package: kdebase-workspace

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

On Debian possible default full paths are:

/usr/bin/ksysguard - from package: ksysguard

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

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