mutiple volume tar

1)create
tar -c -M --tape-length=102400 --file=disk1.tar largefile.tgz

The value 102400 is 1024 x 100, which will create a 100 Meg file called disk1.tar and then Tar will prompt for volume 2 like below :-

Prepare volume #2 for disk1.tar and hit return:

In the time of tape drives you would have taken the first tape out of the machine and inserted a new tape, and pressed return to continue. As we want Tar to create the remaining 50 Meg in a separate file, we issue the following command :-

n disk2.tar





2) merge
#tar -x -M --file=disk1.tar
Prepare volume #2 for `disk1.tar' and hit return: n disk2.tar

method to test disk performance with RAMDisk

cd /tmp

mkdir tmp

mount –t tmpfs tmpfs /tmp/tmp // Create a 24MB ram drive

cp /someFileLessThan24MB /tmp/tmp // Read a large file from MLC to ram drive

mount –t ext2 /dev/ba-nanda1p1 /mnt/banand

sync

time cp /tmp/tmp/someFileLessThan24MB /mnt/banand // Write the large file to banand and measure the timing.

TI EVB rootfs and u-Boot

Easy way to get the target filesystem is mount the ramfs and copy all the files as below:
# gunzip ramdisk_omap2evm.gz --> you will get the unzip ramdisk filesystem file
# mkdir tmp_fs --> create one empty directory
# mount -o loop ramdisk_omap2evm tmp_fs --> mount the ramdisk to this file
# mkdir omap2rootfs
# cp -arf tmp_fs/* omap2rootfs --> now you will have all the rootfilesystem

When debug, easy way is use nfs, also you could use nfsroot to bootup as set the bootargs in uboot as (just for example, make sure the filesystem has been export to enable accessed by NFS):
setenv bootargs 'mem=64M console=ttyS0,115200n8 noinitrd root=/dev/nfs rw nfsroot=192.168.1.98:/nfs/nfsroot,nolock,vers=2,rsize=1024,wsize=1024 ip=dhcp mpurate=266'

gamble

http://blog.sina.com.cn/s/blog_500704190100863e.html

copy minimum file system

find bin etc init sbin var dev home lib usr | cpio -pdum /mnt

legacy power save and triggered power save

The WME method does not allow nonperiodic traffic to use triggered power save; it must use legacy power save instead.

Legacy power save is less efficient than triggered power save

A single trigger frame can retrieve multiple frames in triggered power save
One cannot tell which is the right legacy option to use because TIMs do not indicate how much traffic is buffered, leading to greater inefficiency
PS polls are inefficient if long packet bursts are buffered, as a PS poll is needed for every buffered frame
PM bit (exiting and returning to power save mode) is inefficient for independent frames, as it involves two extra frames for each buffered frame
If the wrong legacy option is chosen, the inefficiency of legacy power save is even greater

By enabling all applications (periodic and nonperiodic) to use the new power save, battery life is extended, as in 802.11e

How to generate subnet host list

perl -e 'for (1...254) {print "10.0.1.$_\n"}' |fping -a -q 2>/dev/null

nmap -sP 10.0.1.0/24