Recently a lot of Mac users are complaining that the software update program is not working correctly and I also ran into this issue today. It just tells you “your software is up to date” but obviously there’s some software not up to date. For example, I opened iTunes and it told me there’s a newer version of iTunes, would you download it? I clicked “download” and the software update app opens but it told me that there’s no update – that made me crazy.
I was not alone. Someone already complained in apple’s support forum. I looked through the replies but found nothing that worked, including deleting com.apple.SoftwareUpdate.plist files. After investigating the problem for minutes, I found that the software update app downloads information from swcdn.apple.com, but the resolved IP for me is not working – as it’s CDN, users at different locations may get different IP addresses.
The solution is simple – add the following line to your /etc/hosts file:
and go back to check software update.
For readers interested in the details, here is the dig result on my machine:
$ dig swcdn.apple.com ; <<>> DiG 9.6.0-APPLE-P2 <<>> swcdn.apple.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18722 ;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 2, ADDITIONAL: 2 ;; QUESTION SECTION: ;swcdn.apple.com. IN A ;; ANSWER SECTION: swcdn.apple.com. 1178 IN CNAME swcdn.apple.com.akadns.net. swcdn.apple.com.akadns.net. 279 IN CNAME swcdn.apple.com.edgesuite.net. swcdn.apple.com.edgesuite.net. 19178 IN CNAME swcdn.apple.com.edgesuite.net.globalredir.akadns.net. swcdn.apple.com.edgesuite.net.globalredir.akadns.net. 279 IN CNAME a1562.ce.w.ytcdn.net. a1562.ce.w.ytcdn.net. 1179 IN A 22.214.171.124 ;; AUTHORITY SECTION: ytcdn.net. 59910 IN NS dns6.expirenotification.com. ytcdn.net. 59910 IN NS dns5.expirenotification.com. ;; ADDITIONAL SECTION: dns5.expirenotification.com. 2803 IN A 126.96.36.199 dns6.expirenotification.com. 377 IN A 188.8.131.52 ;; Query time: 6 msec ;; SERVER: 184.108.40.206#53(220.127.116.11) ;; WHEN: Sat May 15 23:33:33 2010 ;; MSG SIZE rcvd: 305
So ytcdn.net might be an expired domain! Look at its whois information:
Domain Name: ytcdn.net Registrar: XIN NET TECHNOLOGY CORPORATION Whois Server: whois.paycenter.com.cn Referral URL: http://www.xinnet.com Status: clientUpdateProhibited Expiration Date: 2011-04-30 Creation Date: 2008-04-30 Last Update Date: 2010-05-01 Name Servers: dns5.expirenotification.com dns6.expirenotification.com See ytcdn.net DNS Records Information Updated: Sat, 15 May 2010 15:40:22 UTC
Notice that most complaints of software update started in May... I don't know the relationship between ytcdn.net and Akamai CDN, but if ytcdn.net is really expired, it is a serious fault. Apple is using Akamai as its CDN, and Akamai redirects some users to ytcdn.net. As I know, most of these users are in China, but some users in other countries are also affected.
Apple, please contact your CDN provider to solve this problem.