关于/目录的几个问题。

Alex_Sune

/目录必须是rw的吗？如果我把他要w的地方都mount到一个可以w到地方，可以mount成ro的吗？

/目录所在的文件系统必须包含什么？root等目录能不能放在别的文件系统上然后mount上来？

Dragonfly

/ can be ro.
u can mount /etc /usr /root /home /boot from other fs.

Alex_Sune

哦，谢谢Dragonfly。那/下有什么目录是一定会被写的呢？

Dragonfly

bin, sbin, lib, opt, usr, boot, etc  can be ro if u need not install sth or change system configuration. especially for a embedded device

root, home, have to be w if u have user to login into u system.

mnt , is for mount purpose, can be omitted;

proc, and dev are virtual dir, u can mount as ro and try, i am not quite sure,
  
tmp, for tmp files, u can put into /var/tmp

var, for some locks, logs, should be w.


i maybe wrong. so double check pls.  u can read FHS about linux to know more.
a good link is http://www.pathname.com/fhs/

Alex_Sune

从你说的看来，只有root和home有点麻烦，其他的就算是要rw也不是很大。

proc可以是ro的，这一点我确定，因为Magic就是这么做的。

Dragonfly

sometime u can write to sysctl interface to /proc...

Alex_Sune

那Linux对于充当/目录的FS类型有什么要求吗？还是说只要该类FS的支持有直接加进内核就可以？

Dragonfly

i think bootloader have to understand the fs format where u put kernel. so i always put ext3 for that. for /, i think no restriction. but i never try other fs other than ext2, ext3 and reiserfs. and i know fat is possible.

Alex_Sune

情况是这样的，整个系统是要做到一张CD上去的。kernel并不会放到/下面，而是独立的。我是想用cramfs当做/，通过initrd.img的形式加载。

Dragonfly

i think u can check some live cd distributions to see how are they built.

Alex_Sune

刚才看了一下Knoppix里的文档，他是通过一个“mkisofs -R -l -V "KNOPPIX_CN" -hide-rr-moved -v /mnt/sda1/knx/sys/ | create_compressed_fs - 65536 > /mnt/sda1/knx/boot/KNOPPIX”命令生成的。不知道该怎么解压缩。

Alex_Sune

这个文件的前三行是这样的：
#!/bin/sh
insmod cloop.o file=$0 && mount -r -t iso9660 /dev/cloop $1
exit $?

然后接下来的就都是乱码了。

Dragonfly

no, that only build a knoppix cd. u can download one, boot it up, and check each dir rw or ro.

Alex_Sune

这一点倒没有注意。不过他的KNOPPIX是以只读方式挂到“/KNOPPIX”，而“/”只有1.9M，“/bin”、“/sbin”、“/usr”等目录里的文件都是用连接连到“/KNOPPIX”下对应的文件。

Dragonfly

/ can be very small. can u post u df display and its /etc/fstab here? i do not have knoppix at hand. thx