sa: 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/sa - from package: psacct

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

On Debian possible default full paths are:

/usr/sbin/sa - from package: acct

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

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