botti: 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/botti - from package: irssi

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

On Debian possible default full paths are:

/usr/bin/botti - from package: irssi

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

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