reroot: 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/bin/reroot - from package: prime-phylo

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

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