lxc-start: 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/lxc-start - from package: lxc

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

On Debian possible default full paths are:

/usr/bin/lxc-start - from package: lxc

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

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