plm: 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/plm - from package: plm

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

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