svnserve: 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/svnserve - from package: subversion

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

On Debian possible default full paths are:

/usr/bin/svnserve - from package: subversion

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

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