iscsi-readcapacity16: 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/iscsi-readcapacity16 - from package: libiscsi-utils

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

On Debian possible default full paths are:

/usr/bin/iscsi-readcapacity16 - from package: libiscsi-bin

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

Error in other languages:
iscsi-readcapacity16: bevel nie gevind nie
iscsi-readcapacity16: comandă negăsită
iscsi-readcapacity16: comando não encontrado
iscsi-readcapacity16: commande introuvable
iscsi-readcapacity16: command not found
iscsi-readcapacity16: käsku ei ole
iscsi-readcapacity16: không tìm thấy lệnh
iscsi-readcapacity16: komanda nerasta
iscsi-readcapacity16: Kommando nicht gefunden.
iscsi-readcapacity16: kommandot finns inte
iscsi-readcapacity16: komut yok
iscsi-readcapacity16: nie znaleziono polecenia
iscsi-readcapacity16: níor aimsíodh an t-ordú
iscsi-readcapacity16: no se encontró la orden
iscsi-readcapacity16: no s'ha trobat l'ordre
iscsi-readcapacity16: opdracht niet gevonden
iscsi-readcapacity16: parancs nem található
iscsi-readcapacity16: perintah tidak ditemukan
iscsi-readcapacity16: príkaz nenájdený
iscsi-readcapacity16: příkaz nenalezen
iscsi-readcapacity16: команда не найдена
iscsi-readcapacity16: командата не е открита
iscsi-readcapacity16: 命令找不到
iscsi-readcapacity16: コマンドが見つかりません