Root Replacing cacerts

[preempt]

Hi
I wanted to change the cacert file in HTC EVO 4G of /system/etc/security
Did the following steps
# reboot
reboot

C:\android-sdk-windows\tools>adb devices
List of devices attached
HT058HL00699 device


C:\android-sdk-windows\tools>adb shell
# su
su
# mount -o rw,remount -t yaffs2 /dev/block/mtdblock4 /system
mount -o rw,remount -t yaffs2 /dev/block/mtdblock4 /system
# cat /proc/mounts
cat /proc/mounts
rootfs / rootfs ro 0 0
tmpfs /dev tmpfs rw,mode=755 0 0
devpts /dev/pts devpts rw,mode=600 0 0
proc /proc proc rw 0 0
sysfs /sys sysfs rw 0 0
tmpfs /sqlite_stmt_journals tmpfs rw,size=4096k 0 0
none /dev/cpuctl cgroup rw,cpu 0 0
/dev/block/mtdblock4 /system yaffs2 rw 0 0
/dev/block/mtdblock6 /data yaffs2 rw,nosuid,nodev 0 0
/dev/block/mtdblock5 /cache yaffs2 rw,nosuid,nodev 0 0
tmpfs /app-cache tmpfs rw,size=8192k 0 0
/dev/block//vold/179:1 /sdcard vfat rw,dirsync,nosuid,nodev,noexec,uid=1000,gi
1015,fmask=0702,dmask=0702,allow_utime=0020,codepage=cp437,iocharset=iso8859-1
hortname=mixed,utf8,errors=remount-ro 0 0

# cd /sdcard/
cd /sdcard/

# ls -l
ls -l
d---rwxr-x system sdcard_rw 2010-04-09 15:38 HTC Sync
d---rwxr-x system sdcard_rw 2010-04-09 15:39 Music
d---rwxr-x system sdcard_rw 2010-04-09 15:39 Sample Photo
d---rwxr-x system sdcard_rw 1980-01-06 00:00 LOST.DIR
d---rwxr-x system sdcard_rw 2010-05-20 11:04 rssreader
d---rwxr-x system sdcard_rw 2010-11-14 16:45 albumthumbs
d---rwxr-x system sdcard_rw 2010-05-20 11:19 rosie_scroll
d---rwxr-x system sdcard_rw 2010-06-12 14:16 tmp
d---rwxr-x system sdcard_rw 2010-05-20 12:48 Android
d---rwxr-x system sdcard_rw 2010-11-16 12:19 DCIM
d---rwxr-x system sdcard_rw 2010-09-12 15:04 download
d---rwxr-x system sdcard_rw 2010-05-20 17:45 media
d---rwxr-x system sdcard_rw 2010-05-20 22:10 Downloads
----rwxr-x system sdcard_rw 55715 2010-11-17 16:06 cacerts.bks
d---rwxr-x system sdcard_rw 2010-05-23 00:38 agilefusion
d---rwxr-x system sdcard_rw 2010-05-23 11:15 Qik
d---rwxr-x system sdcard_rw 2010-05-25 08:46 thumbs
----rwxr-x system sdcard_rw 55715 2010-11-15 18:39 new-cacerts.bks
----rwxr-x system sdcard_rw 535540 2010-11-17 15:21 busybox


# dd if=/sdcard/new-cacerts.bks of=./cacerts.bks
dd if=/sdcard/new-cacerts.bks of=./cacerts.bks
108+1 records in
108+1 records out
55715 bytes transferred in 0.018 secs (3095277 bytes/sec)

# cd /system/etc/security
cd /system/etc/security
# ls -l
ls -l
-rw-r--r-- root root 1107 2010-04-28 19:10 otacerts.zip
-rw-r--r-- root root 55715 2010-04-28 08:54 cacerts.bks

# df
df
/dev: 201900K total, 0K used, 201900K available (block size 4096)
/sqlite_stmt_journals: 4096K total, 4K used, 4092K available (block size 4096)
/system: 358400K total, 217796K used, 140604K available (block size 4096)
/data: 437888K total, 85680K used, 352208K available (block size 4096)
/cache: 163840K total, 1416K used, 162424K available (block size 4096)
/app-cache: 8192K total, 1092K used, 7100K available (block size 4096)
/sdcard: 7753728K total, 132032K used, 7621696K available (block size 32768)

# dd if=/sdcard/new-cacerts.bks of=./cacerts.bks
dd if=/sdcard/new-cacerts.bks of=./cacerts.bks
./cacerts.bks: write error: No space left on device
42+0 records in
41+0 records out
20992 bytes transferred in 0.384 secs (54666 bytes/sec)

It fails to transfer the entire file even if the space is available.I tried to replace the same file as well it fails
can anyone guide me to change the cacert file