2007-Dec-25 - Things to consider after a fix

From "Why Programs Fail".

1. Does the failure no longer occur? (There may be second cause.)

2. Does the fix introduce new problems?

3. Is there same mistake elsewhere? (The same developer, same APIs.)

4. Is the change committed? (Version control, bug track.)

2007-Dec-25 - How to ... (Linux version)

1. How to add a user on Unix platform:

# useradd {user_name}

# more /etc/passwd                   --> Here {user_name} should has been added.

# passwd {user_name}             --> Here set a password for {user_name}

2. How to set DNS in Linux:

Modify file /etc/resolv.conf

3. How to modify locale in Linux:

1) To check current locale, run command: locale

2) localedef -f GB2312 -i zh_CN zh_CN.gb2312

--> /usr/lib/locale should has been added "zh_CN.gb2312"

     /usr/lib/gconv/gconv-modules includes "alias GB2312-1980// EUC-CN//"

3) export LC_ALL=zh_CN.gb2312

4) To verify, run command: date

--> It should display Chinese.

5) To automatically enter Chinese locale in the next boot, add the following two lines in file /root/.bashrc:

export LANG=zh_CN.gb2312

export LC_ALL=zh_CN.gb2312

4. How to change the default booting Operating System:

1) Open /boot/grub/grub.conf (menu.lst)

2) Modify "default #..."

5. How to set IP - hostname list in Linux:

/etc/hosts:

{ip}    {host_name(FQDN/long name)}    [short name]

6. How to change the listening port of Postfix:

1) /etc/postfix/master.cf:

Change

    smtp inet n - n - - smtpd

to

    mysmtp inet n - n - - smtpd

2) /etc/services:

Add

    mysmtp {port_number}/tcp mail

3) Restart postfix:

/etc/init.d/postfix restart

7. How to config IP in Linux:

/etc/sysconfig/network/ifcfg-eth-...:

Configure IPADDR and BOOTPROTO

8. How to add perl modules:

Precondition: Perl & modules installed.

# /usr/local/ActivePerl-5.8/bin/ppm

rep off 1                     --> To turn of the default modules. Optional.

rep off 1

rep add {module_name} "{module_path}"

search *

install n                    --> n is the No. of the module that you want to install.(eg. install 1, 2, 7) 

9. How to have a quick test on handle leak:

# ps -ef | grep processname                     --> Check the process ID that needs to test handle leak.

# cd /proc/{PID}/fd/

# ll                                              --> Check socket number

Compare with the current connection number to see whether there's handle leak.

10. How to compile and run a C program:

# gcc -o output_filename program_name.c     --> compile

# ./output_filename                                        --> run

11. How to enable core dump:

# ulimit -c unlimited

Note: run "ulimit -c" to check whether it's enabled. If it returns "0", it is disabled; If it returns "unlimited" or some other number (the core dump file size), it is enabled.

12. How to calculate the total number of files under a folder:

# ll | wc -l

13. How to check cpu info:

# cat /proc/cpuinfo

14. How to configure Xdm on Linux for remote Xwindows access?

1) Modify /etc/X11/xdm/xdm-config:
  "DisplayManager.requestPort:    0"---> "!DisplayManager.requestPort:    0"
2) Modify Xaccess:
"#*    #any host can get a login window" -->"*    #any host can get a login window"
3) Modify Xservers:
":0 local /usr/X11R6/bin/X" -->"#:0 local /usr/X11R6/bin/X"
4) run 'xdm'
5) then you can use Xmanager or X-Win32 to connect it.

Note: If on Suse, to configure Xdm for ROOT remote login:

1) Modify /etc/pam.d/login:

  "auth required pam_securetty.so" --> "# auth ..."

2) Modify /etc/sysconfig/displaymanager:

  DISPLAYMANAGER_REMOTE_ACCESS="yes"

  DISPLAYMANAGER_ROOT_LOGIN_REMOTE="yes"

15. How to test code coverage:

Command: gcov

1) When compile with gcc command, add arguments fprofile-arcs and ftest-coverage

eg. #gcc -g -o output_name input.c -fprofile-arcs -ftest-coverage

2) Run output_name

3) #gcov input.c

Now input.c.gcov file is created. Use "less" command to view the gcov file. The lines following ##### were not executed in the step 2) run.

2007-Dec-6 - Linux Performance Monitoring - study notes

2007-Nov-23 - Trouble shooting ... (network & apps)

Windows:

1. Domain name resolution error while sending a mail.

# ping {domain_name}

-> Return corresponding IP1, correct.

But

# nslookup {domain_name}

-> Return IP2, incorrect.

Troubleshoot:  (>> input ;  << output)

1) >> ipconfig /all

    << Windows IP configuration & Ethernet adapter Local Area Connection

2) >> nslookup

    << Default Server & address

    >> server {DNS_IP}                    -- Here reset the correct DNS server IP.

    << Default Server & address

    >> IP1

    << The corresponding domain_name       -- This step checks whether the DNS is correct.

3) Disable and enable network connection if anything changed.

2. Java Applet load failed.

1) Install MSJav

2) Open Internet Options -> Advanced, uncheck Java (Sun) and check MS VM.

3. HTTP download failed or file not found.

a. Check IIS (http server) privilege. Add everyone if necessary.

b. Add MIME Types:

Open IIS, open Default Web Site Properies -> HTTP Headers -> MIME Types -> New:

.*       application/octet-stream

4. Failed to connect to http server. (Unauthorized.)

a. Open IIS, open Default Web Site -> Properties -> Directory Security -> Authentication and access control. Click Edit. Check Enable anonymous access.

Or b. Type username and password in client.

5. Windows 2003 + IIS 6.0 "Service Unavailable" error.

Open IIS, then open Web Sites -> Properties -> Service. Check "Run WWW service in IIS 5.0 isolation mode". 

6. VMWare failed to launch peer process.

Probably caused by low disk space. Free some space, and stop all vmware related processes, then try again.

7. VMWare Station not able to take snapshot (the menu is grayed).

It's because the VM is created by old version of VMWare.

Select VM->Upgrade Virtual Machine.

Linux:

1. "ifconfig" command does not work in Turbo linux when remote access by PuTTY.

Change the Keyboard setting in PuTTY: select Control-H, rxvt, SCO.

2. Failed to access Suse linux by PuTTY.

Change the SSH authentication type:

Config -> SSH -> Auth: check SSH1. 

3. Postfix only binds to localhost (127.0.0.1).

1) Open /etc/postfix/main.cf

2) Search for: inet_interfaces = localhost 

3) Change it to: inet_interfaces = All

4. Program make/build error: Makefile is older than Makefile.org, Configure or config. (Error code 1)

Probably caused by lagging system time. Just change system time to current and try again.

2007-Oct-29 - File descriptor and convention of Windows and Unix platform

When port web application to IIS, developer has to do the following conversion on his codes, so that the Unix files meet Windows convention. QA hence need to pay attention to these points too.

Feature	Unix Implementation	Change to Windows Implementation
Directory separator	Forward slash (/).	Backslash(＼)。 Note: In Perl script, backslash is used as an excape character. So you have to use double backslash(＼＼) to indicate the backslash in a directory.
File names and pathnames	Unix supports long file name and extension with 4 characters. File name is case sensitive.	FAT file system uses DOS 8.3 filename convention. And it's case insensitive. NTFS is case aware, yet case insensitive.
Directory hierarchy	Unix file system appears as a single directory layer.	Windows storage is seperated to several physical and virtual drives, each of which has a directory hierarchy. So you have to specify the drive letter(C,D,E,etc.) as part of the file path when access a Windows file.
Text file line termination	Unix only uses LF(line feed) to indicate the end of a line in text file.	Uses both CR(carriage return) and LF to terminate a line in text file, and some applications.
File desciptors/handles	Unix file descriptors 0, 1, and 2 indicate stdin, stdout, and stderr respectively.	Win32 uses handles instead of descriptors. Call Win32 API GetStdHandle() to confirm which handle is in use.

File path length limitation

Unix filename is restricted to 255 characters.

Windows file path is restricted to 259 characters.