How to search a keyword in a folder

$ grep -rl "string" /someone_folder

Provide a sftp account but disable it's SSH access for a team member

[Target]
1. Using user 'sftp-user'
2. Store files on folder '/sftp-folder'
3. Allow a team member to access it
4. Using RSA public key for access control

[Step]
1. Prepare account 'sftp-user' and folder '/sftp-folder'
   Create a user 'sftp-user'
   Create a folder 'sftp-folder' on /
   Change the folder owner to root; 'chown root /sftp-folder'

2. Modify SSHd setting, edit /etc/ssh/sshd_config

  sudo vi /etc/ssh/sshd_config

================================================================
#Subsystem sftp /usr/lib/openssh/sftp-server
Subsystem sftp internal-sftp

Match user sftp_user
  ChrootDirectory /sftp_folder
  AllowTcpForwarding no
  X11Forwarding no
  ForceCommand internal-sftp
=================================================================

3. To disable SSH for sftp-user
Modify /etc/passwd, change account 'sftp-user' shell program to /bin/false from /bin/bash

  sudo vi /etc/passwd

4. Edit permission list
Add RSA public keys to /home/sftp-user/.ssh/authorized_key

5. restart SSHd

  sudo /etc/init.d/ssh restart

[TEST]
You can generate a RSA public key on someone Linux, and provide it to sftp administrator.
After your key added to sftp-user's authorized_key file, you can using sftp to connect 'sftp-user' account

  sftp sftp-user@somehome.com

How replace old 'master' branch with new 'master' branch

Sometime, the master's commits was arranged with 'rebase' and the master branch has new commits.
How to update commits of new master branch to remote repository's master branch

  $ git push --force origin master

If the arranged branch isn't 'master', need to rename 'master' to other name, like 'old_master',
than rename arranged branch to 'master', and push with --force parameter.

  $ git branch -m master old_master
  $ git branch -m new_master master
  $ git push --force origin master

Using meld for git diff

* 建立一個給git diff用的script file 在/usr/local/bin/git-meld

    #!/bin/sh
    #This file placed at /usr/local/bin/git-mled

    meld $2 $5

* 設定git diff 用的外部程式

    git config --global diff.external /usr/local/bin/git-meld

* 要恢復預設的git diff 方式

    git config --global -unset diff.external

Using script file to mount ecryptfs file system

#!/bin/sh

echo 'passwd=12345678' > /tmp/mypasswd.txt

sudo mount -t ecryptfs test_ec test_ec -o \
key=passphrase:passfile=/tmp/mypasswd.txt,\
ecryptfs_cipher=aes,\
ecryptfs_key_bytes=16,\
ecryptfs_passthrough=y,\
ecryptfs_fnek_sig=617264405cf6d2f2

rm /tmp/mypasswd.txt

Git 簡單指令使用

* 建立git database
$ git init

* 建立第一個進度點/版本(commit)
$ git add .
$ git commit -m "initial"

* 比對
$ git diff master
* 產生patch
$ git diff master > xxx.patch

* 放棄修改, 恢復到目前的commit
$ git checkout -f

* 列出commit
$ git log --pretty=oneline

14b26e3e80941f8290019f63231fb8b03ff805c1 initial

* 給予標籤
$ git tag -a v0.1  14b26e



========================================
* 使用patch
patch -p1 < xxx.patch

A problem about the character 0xD is be changed to 0xA

== LF/CR issue with RS232 in Linux ==

stty -F /dev/ttyS0 -onlcr

stty -F /deb/ttyS0 -icrnl

Redirect stderr to file

IO index is:
1 is stdout
2 is stderr

===Redirect stderr to 'log.txt' file===

$ someprogram  2> log.txt

===Redirect stderr to stdout===

$ someprogram 2>&1 | less

===Redirect stderr and stdout to a file===

$ someprogram &> log.txt

Enable telnetd service

• Install package

for Ubuntu or debain
# sudo apt-get install xinetd telnetd
or
for Angstrom Distribution
# opkg install netkit-telnet xinetd

• Edit /etc/xinetd.conf

# vi /etc/xinetd.conf

defaults
{
        instances = 60
        log_type = SYSLOG authpriv
        log_on_success = HOST PID
        log_on_failure = HOST
        cps = 25 30
}
includedir /etc/xinetd.d

• Edit /etc/xinetd.d/telnet

# vi /etc/xinetd.d/telnet

service telnet
{
        disable = no
        flags = REUSE
        socket_type = stream
        wait = no
        user = root
        # server = /usr/sbin/in.telnetd
        server = /usr/sbin/telnetd
        log_on_failure += USERID
}

• Execute xinitd service

# /etc/init.d/xinetd restart

SDIO clock

You can find the command for setting sdio clock

mmc_sdio_init_card() in /drivers/mmc/core/sdio.c

wireless and bluetooth modules

insmod /lib/modules/2.6.32/kernel/net/rfkill/rfkill.ko
insmod /lib/modules/2.6.32/kernel/net/wireless/cfg80211.ko
insmod /lib/modules/2.6.32/kernel/net/wireless/lib80211.ko
insmod /lib/modules/2.6.32/kernel/net/wireless/lib80211_crypt_ccmp.ko                                        
insmod /lib/modules/2.6.32/kernel/net/wireless/lib80211_crypt_tkip.ko                                        
insmod /lib/modules/2.6.32/kernel/net/wireless/lib80211_crypt_wep.ko
insmod /lib/modules/2.6.32/kernel/net/mac80211/mac80211.ko


insmod /lib/modules/2.6.32/kernel/net/rfkill/rfkill.ko                        
insmod /lib/modules/2.6.32/kernel/net/bluetooth/bluetooth.ko
insmod /lib/modules/2.6.32/kernel/drivers/bluetooth/btmrvl.ko
insmod /lib/modules/2.6.32/kernel/drivers/bluetooth/btmrvl_sdio.ko

To create a image file for new space

// create a 1G image file
# dd if=/dev/zero of=1G.img bs=1M seek=1024 count=0

# ls -l 1G.img
-rw-r-r- 1 root  root  1048576000 Mar 25 15:32 1G.img

# du -m 1G.img

//format the 1G image file as ext3 format
# sudo mkfs.ext3 -L LABELIMAGE ./1G.img

# sudo mount -t ext3 ./1G.img /mnt/image -o loop