lsblk: 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:

/bin/lsblk - from package: util-linux-ng

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

On Debian possible default full paths are:

/bin/lsblk - from package: util-linux

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

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