check_lft_balance: 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 Debian possible default full paths are:

/usr/sbin/check_lft_balance - from package: infiniband-diags

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

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