irqbalance: 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/irqbalance - from package: irqbalance

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

On Debian possible default full paths are:

/usr/sbin/irqbalance - from package: irqbalance

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

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