tr: 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/bin/tr - from package: coreutils
/var/spool/hylafax/bin/dict/tr - from package: hylafax+

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

On Debian possible default full paths are:

/usr/bin/tr - from package: coreutils
/usr/lib/plan9/bin/tr - from package: 9base

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

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