tgtadm: 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/tgtadm - from package: scsi-target-utils

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

On Debian possible default full paths are:

/usr/sbin/tgtadm - from package: tgt

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

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