Python Sudoku solver

I played sudoku a couple of times and found it interesting, but it is really time cosuming to solve it by human. One biggest problem is human brian is not capable of storing many solution trials. So I wrote a this program to solve it with brutal force. Well it takes a fraction of a second to solve any valid sudoku puzzels.

The following is the solver in python:

 

Partial backup

IMHO, traditional full backup (image backupfrom one disk to another or tape) does not make much sense because:

Check MX record and black list

Administrate an Email server

This section includes installation and maintenance of a email server.

The email server will have the following features:

  • POP/IMAP
  • SMTP with user authentication and TSL encryption
  • Web mail (supports login to other IMAP servers)
  • Spam filter

vmstat "wa" reports high value, why?

When I was doing performance tunning, I use vmstat to see memory and CPU usage and look for the bottleneck just like other sysadmins.

 

I see something like this:

Fix "rcmd: socket: Permission denied"

When expanding my old cluster, I see error "rcmd: socket: Permission denied" when rsh to the master node as normal user. User root works fine and rsh running a command is also fine.

it turned out to be the rlogin permission problem. When rsh to an interactive shell, it calls rlogin. The rlogin command must have "s" bit on the owner root.  Use 'chmod 4755 /usr/bin/rlogin' to fix the permissions.

Strace a process

strace -tt -o logfile -p PID

Full system backup

Restore from a full system backup is the fastest way to recover the service in case of a disastrous system failure.

There are many ways to do full system backups and commercial software is also available.

Resume a partial copy or download

Command cp, scp and wget don't support partial copy and resume.

Curl is an alternative command line tool in this situation. Example of usage:

curl -C - -O file:///home/jmao/smbmount/My\ Movies/10_years_of_thomas.iso

SGE test and some simple manage commands

Login as a user that is allowed to submit job with SGE. Refer to "User Access" under "Queue Control" for more information if this part isn't clear.

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