Peter Wang’s Weblog

All partitions of our Linux-based server suddenly went read-only, all write operations failed with “Read-only filesystem” error. I had never seen such strange problem before, after some Google search, I reached the conclusion that it might be caused by some serious hard disk issues.

It’s 3:00 am, and I had no choices but go to data center to fix that server by myself. It’s such a terrible experience, luckily, the problem got fixed finally.

Here are the steps I took:

1) I guess the problem was caused by some hard disk issues, and running fsck may have a chance fixing it

2) pressing the ‘reset’ button, after a few seconds, SUSE(SUSE Linux Enterprise Server 11) boot failed, and dropped a prompt asking for root password

3) inputting root password to enter safe-mode, we can run fsck to fix the filesystem of all partitions. we use ext3, so run fsck -t ext3 /dev/sda[n] on each partition.

4) Luckily, all filesystems were repaired successfully, Ctrl+D to exit the safe-mode shell, system rebooted.

5) everything went OK.

Many various issues may lead to such problem, these steps work for my particular situation, I can’t guarantee them work for yours. There is NO WARRANTY, run it on your own risk.

If only maintaining several crontab entries, `crontab -e’ way is sufficient and straight forward. However, any non trivial website may have a large number of crontab entries to be maintained, and keeping these entries as files that tracked with VCS seems a better solution.

Most GNU/Linux distributions keep system-wide crontab entries in /etc/init.d directory. Two points that need to keep in mind here are:
a) owner of files in /etc/init.d must be root
b) files are reloaded when /etc/init.d is modified or files are modified

so we can use either way of:
1) check out crontab entry from repos, then chown root.root /file/in/repos, ln -sf /file/in/repos /etc/cron.d/file
2) check out crontab entry from repos, then chown root.root /file/in/repos, rsync /file/in/repos /etc/cron.d/file

at the end, the format of files in /etc/cron.d is like following

* * * * * root /path/to/script > /dev/null 2>&1

People can use free wifi in beijing capital airport t3 to surf the internet now.

First connect the wifi-enabled devices to the “airport free wifi”, a wifi AP, then open a browser and visit some website, a window will pop-up asking for the username and password, which can be gained by filling your mobile phone number that can be used to receive them later. As long as you get your username/password you can use them to start your internet surfing.

The only drawback of the free wifi is its instability. During my trial, it got disconnected several times, and sometimes it could be very slow, probably because too many people are using it. After all, free is good.

This blog had just Upgraded to WordPress 3.1 from 2.5, The upgrade process is smooth, since none customized plugins/themes were used.

WordPress 3.1 is great! I will write more frequently from now on, i guess.

Just for test

“alt + enter” by default toggles fullscreen mode, we can rebinding it as follows:

1. click menu: Tools-> Keymap Editor

2. click “Map a Key”, and press “Alt + Enter”

3. select “Send String”, and input \033\015, and click ok

4. click save, and close.

5. now, alt + enter send M-RET in emacs.