e2undo: 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/e2undo - from package: e2fsprogs

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

On Debian possible default full paths are:

/sbin/e2undo - from package: e2fsprogs
/usr/lib/debug/sbin/e2undo - from package: e2fsprogs-dbg

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

Error in other languages:
e2undo: bevel nie gevind nie
e2undo: comandă negăsită
e2undo: comando não encontrado
e2undo: commande introuvable
e2undo: command not found
e2undo: käsku ei ole
e2undo: không tìm thấy lệnh
e2undo: komanda nerasta
e2undo: Kommando nicht gefunden.
e2undo: kommandot finns inte
e2undo: komut yok
e2undo: nie znaleziono polecenia
e2undo: níor aimsíodh an t-ordú
e2undo: no se encontró la orden
e2undo: no s'ha trobat l'ordre
e2undo: opdracht niet gevonden
e2undo: parancs nem található
e2undo: perintah tidak ditemukan
e2undo: príkaz nenájdený
e2undo: příkaz nenalezen
e2undo: команда не найдена
e2undo: командата не е открита
e2undo: 命令找不到
e2undo: コマンドが見つかりません