ubuntu14.04にてpxeブートのディスクレス環境を構築しています. 構築しているのはdns, dhcp, nfs, ldapサーバで全てバージョンは14.04です.
起動することには成功したのですが, ldapクライアントを導入すると起動が極端に遅くなってしまう現象が発生しました.
ldapクライアントを導入前には順調に起動します.

ldap導入後のdmesg.logで遅くなっている箇所は以下のようになっています.
[   15.531369] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[   18.899347] random: nonblocking pool is initialized
[  129.013625] init: plymouth-upstart-bridge main process (243) terminated with status 1
[  129.013785] init: plymouth-upstart-bridge main process ended, respawning
[  169.214184] init: plymouth-upstart-bridge main process (251) terminated with status 1
[  169.215218] init: plymouth-upstart-bridge main process ended, respawning
[  169.234131] init: plymouth-upstart-bridge main process (256) terminated with status 1
[  169.234227] init: plymouth-upstart-bridge main process ended, respawning
[  169.243686] init: plymouth-upstart-bridge main process (260) terminated with status 1
[  169.243791] init: plymouth-upstart-bridge main process ended, respawning
[  169.253108] init: plymouth-upstart-bridge main process (262) terminated with status 1
[  169.253207] init: plymouth-upstart-bridge main process ended, respawning
[  169.261885] init: plymouth-upstart-bridge main process (264) terminated with status 1
[  169.261982] init: plymouth-upstart-bridge main process ended, respawning
[  169.271560] init: plymouth-upstart-bridge main process (265) terminated with status 1
[  169.271658] init: plymouth-upstart-bridge main process ended, respawning
[  169.280913] init: plymouth-upstart-bridge main process (267) terminated with status 1
[  169.281011] init: plymouth-upstart-bridge main process ended, respawning
[  169.290858] init: plymouth-upstart-bridge main process (268) terminated with status 1
[  169.290955] init: plymouth-upstart-bridge main process ended, respawning
[  169.300736] init: plymouth-upstart-bridge main process (270) terminated with status 1
[  169.300833] init: plymouth-upstart-bridge main process ended, respawning
[  169.310384] init: plymouth-upstart-bridge main process (271) terminated with status 1
[  169.310489] init: plymouth-upstart-bridge main process ended, respawning
[  169.320939] init: plymouth-upstart-bridge main process (273) terminated with status 1
[  169.321044] init: plymouth-upstart-bridge respawning too fast, stopped
[  174.924402] systemd-udevd[402]: starting version 204

bootchartを見てみると止まっている時間の多くはhostnameがzombieプロセスとしてあります.
また，dhcpの/etc/dhcp/dhcp.confに起動するクライアントのipアドレスとホスト名を割り当てない
(/etc/dhcp/dhcp.confの中のgroup disklessを消す)と上記の待ち時間が10秒程度になることがわかっています.

dhcpの設定の/etc/dhcp/dhcp.confは
subnet 203.0.113.0 netmask 255.255.255.0
{
    default-lease-time          3600;
    max-lease-time              3600;
    option domain-name          "domain";
    option subnet-mask          255.255.255.0;
    option routers              ip;
    option domain-name-servers  ip;
    range                       ip;

    # network boost options
    next-server     ip;　　　　　　　　　　//pxeサーバ
    filename        "/pxelinux.0";
}

group diskless                //起動するマシンに与えるipアドレス
{
    default-lease-time  86400;
    max-lease-time      86400;
    use-host-decl-names on;

    host name { hardware ethernet aa:bb:cc:dd:ee:ff; fixed-address ip; }
}

ldapとdhcpに特別な設定を与える必要があるのでしょうか. それとも起動するOS側の設定が不足しているのでしょうか
何かアドバイスいただけませんでしょうか。よろしくお願いいたします。