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user69453
Asked: 2014-06-16 14:47:37 +0800 CST

Deleting update cache

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How can I clear the list of updates and softwares (from an ubuntu download server) created when sudo apt-get update is run for the first time (after the download server is selected)?

I do not want to delete the downloaded .deb files just the update cache created by sudo apt-get update.

package-management

1 Answers

  1. Best Answer

    • Downloaded package lists are in:

      /var/lib/apt/lists/

      Reference: The Debian Administrator's Handbook - The apt-cache Command

    • You can get that easily with strace command:

      strace -e trace=open apt-get update

      Meaning: trace file open system calls of apt-get update

    • strace - trace system calls and signals

      strace is a useful diagnostic, instructional, and debugging tool. System administrators, diagnosticians and trouble-shooters will find it invaluable for solving problems with programs for which the source is not readily available since they do not need to be recompiled in order to trace them.

      Students, hackers and the overly-curious will find that a great deal can be learned about a system and its system calls by racing even ordinary programs. And programmers will find that since system calls and signals are events that happen at the user/kernel interface, a close examination of this boundary is very useful for bug isolation, sanity checking and attempting to capture race conditions.

      Usage: strace [trace_options] command [args]

      So:

      1. apt-get update is the regular command used to update/download packages lists.
      2. strace will run apt-get update and trace its system calls.
      3. -e trace=open strace with default options will log all system calls. But we don't need that. So with this option strace will trace only file opening calls/operations.

      Reference: man strace

      Output sample:

      strace -e trace=open apt-get update > /dev/null

      open("/tmp/fileutl.message.WrgKYY", O_RDWR|O_CREAT|O_EXCL, 0600) = 17
open("/var/lib/apt/lists/extras.ubuntu.com_ubuntu_dists_trusty_Release", O_RDONLY) = 19
open("/var/lib/apt/lists/extras.ubuntu.com_ubuntu_dists_trusty_Release", O_RDONLY) = 17
open("/tmp/fileutl.message.TrxfHl", O_RDWR|O_CREAT|O_EXCL, 0600) = 17
open("/var/lib/apt/lists/dl.google.com_linux_chrome_deb_dists_stable_Release", O_RDONLY) = 19
open("/var/lib/apt/lists/dl.google.com_linux_chrome_deb_dists_stable_Release", O_RDONLY) = 17
open("/tmp/fileutl.message.gaI8CI", O_RDWR|O_CREAT|O_EXCL, 0600) = 17
open("/var/lib/apt/lists/dl.google.com_linux_talkplugin_deb_dists_stable_Release", O_RDONLY) = 19
open("/var/lib/apt/lists/dl.google.com_linux_talkplugin_deb_dists_stable_Release", O_RDONLY) = 17
open("/tmp/fileutl.message.fcWaM5", O_RDWR|O_CREAT|O_EXCL, 0600) = 17
open("/var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_trusty-security_Release", O_RDONLY) = 19
open("/var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_trusty-security_Release", O_RDONLY) = 17
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