mklost+found: 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/sbin/mklost+found - from package: e2fsprogs

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

On Debian possible default full paths are:

/usr/sbin/mklost+found - from package: e2fsprogs
/usr/lib/debug/usr/sbin/mklost+found - from package: e2fsprogs-dbg

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

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