2 questions about emulating sdcard

[MarcusHe]

1. Notwithstanding selecting a 256M SD card when creating AVD in eclipse AVD manager, should I use tools\mksdcard to create a sdcard.img???What's the diffrence???
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[FONT=宋体]Environment: [/FONT]
[FONT=宋体]Ubuntu10.04,JDK1.7,Natvie android SDK 2.2 download from google official website[/FONT]

2. when I push a WuBai.mp3 file to emulator , it is indicating [FONT=&#23435]“[/FONT]failed to copy [FONT=&#23435]。。。。。[/FONT]read-only file system[FONT=&#23435]”。[/FONT] Thus I did below actions on ubuntu10.04 and get the same result:
a. tools/mksdcard 256M sdcard.img to create a sd-card image file. Ensure it is writable and readable
b. mkdir SDCard to build a folder which will hold content
c. sudo mount –o loop sdcard.img SDCard
d emulator –avd MyAVD –sdcard ./sdcard.img –scale 0.6
[FONT=宋体]I've tried DDms and adb push command , same results. [/FONT]
[FONT=宋体]on ddms-->File explorer , i find 3 main directories are "system,data,mnt" , while on Window OS, these 3 directories are "system,data,sdcard". Why??[/FONT]
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I searched on web sites yesterday and found nothing help. Most of them emulate sdcard on Windows, instead of on linux or Ubuntu. I[FONT=&#23435]’[/FONT]ve tried emulating on Windows, all work well.
Can anyone figure out?

 

[MarcusHe]

Very Very Strange!!! I just now tried again ,find ddms can push file while "adb push " can't work still. But this time , i don't mount anything ,just emulator -sdcard sdcard.img -avd MyAVD .
I notice one diffrence :
Yesday: there are only secure and lost.dir folder under /mnt
Today : They are asec,sdcard,secure under /mnt
What's going on??!!

 

[MarcusHe]

I tried emulator without sdcard.img , ddms still can push a file and /mnt/sdcard is still visible.
Did i misunderstand something ??