[email protected]:~# sudo apt-get install php5-curl
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
libcurl3
The following NEW packages will be installed:
libcurl3 php5-curl
0 upgraded, 2 newly installed, 0 to remove and 75 not upgraded.
Need to get 263 kB of archives.
After this operation, 725 kB of additional disk space will be used.
Do you want to continue [Y/n]? y
Err http://us.archive.ubuntu.com/ubuntu/ oneiric-updates/main libcurl3 i386 7.21.6-3ubuntu3.2
Temporary failure resolving 'us.archive.ubuntu.com'
Err http://security.ubuntu.com/ubuntu/ oneiric-security/main libcurl3 i386 7.21.6-3ubuntu3.2
Temporary failure resolving 'security.ubuntu.com'
Err http://security.ubuntu.com/ubuntu/ oneiric-security/main php5-curl i386 5.3.6-13ubuntu3.3
Temporary failure resolving 'security.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/pool/ ... 2_i386.deb Temporary failure resolving 'security.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/pool/ ... 3_i386.deb Temporary failure resolving 'security.ubuntu.com'
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
[email protected]:~#

域名解析出现错误。
你换个域名服务器试试，比如google提供的8.8.8.8