mktexlsr: 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/mktexlsr - from package: texlive

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

On Debian possible default full paths are:

/usr/bin/mktexlsr - from package: texlive-binaries

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

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