lslk: 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/sbin/lslk - from package: lslk

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

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