systemsettings: 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/systemsettings - from package: kdebase-workspace

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

On Debian possible default full paths are:

/usr/bin/systemsettings - from package: systemsettings

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

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