snice: 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/snice - from package: procps

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

On Debian possible default full paths are:

/usr/bin/snice - from package: procps

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

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