psmerge: 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/psmerge - from package: psutils-perl

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

On Debian possible default full paths are:

/usr/bin/psmerge - from package: psutils

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

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