renice: 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/renice - from package: util-linux-ng

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

On Debian possible default full paths are:

/usr/bin/renice - from package: bsdutils

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

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