blkdeactivate: 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:

/sbin/blkdeactivate - from package: lvm2

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

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