iosnoop: 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 Debian possible default full paths are:

/usr/bin/iosnoop - from package: perf-tools-unstable

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

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