fsck: 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/fsck - from package: util-linux-ng

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

On Debian possible default full paths are:

/sbin/fsck - from package: util-linux

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

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