slabtop: 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/slabtop - from package: procps

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

On Debian possible default full paths are:

/usr/bin/slabtop - from package: procps

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

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