mergesolv: 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/mergesolv - from package: libsolv-tools

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

On Debian possible default full paths are:

/usr/bin/mergesolv - from package: libsolv-tools

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

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