Name: Fabrice Bellet
Member since: 2004-07-07 17:53:29
Last Login: 2011-12-20 19:50:32
I'm always impressed by how significant can be the speed improvement of a typical linux desktop, when just replacing a disk with classic rotational platters, by a solid state drive. The boot is immediately faster, the desktop applications appear almost immediately on screen, ditto for icons in the menu bar. Clearly a huge bottleneck disappears, and the processor is consequently used more intensively. Few years ago, we used to say that adding more memory was a good way to give a second youth to an aged linux box, nowadays putting a solid state drive in the box is an even better way.
During the migration of my build system for fedora packages, from plague to koji, I set up all the machines needed by this infrastructure as virtual boxes. This is interesting for builder machines, as it is possible to adjust their dedicated resources dynamically, depending on the number of packages to be built by the system. Unfortunately, I've quickly been bitten by a recurring bug in my kvm builders : as soon as they are configured with more than one virtual processor, processes begin to stall, the virtual machine becomes unresponsive, although there's no sign of abnormal disk, net, or cpu activity.
After some research, looking for the "soft lockup" expression that the guest kernel puts in the log files, which seems to be a rather common cause of problems, I narrowed the possibilities down to the clock source being used in the guest kernel. Booting with "clocksource=acpi_pm", and forcing the use of this clock source provided much more stability in my VM so far...
# echo acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource
The gnome-keyring-daemon is now a drop-in replacement for ssh-agent. Until recently, I faced with several situations where the daemon silently crashes and all the ssh keys already loaded in the agent are lost. The way I use ssh is quite intensive, for example I'm a big fan of pdsh, the command dedicated to launch a command to a group of machines in parallel. Every machine is reached via ssh, so the ssh agent is heavily solicited when pdsh is executed. I suspected some bad data structures locking in the agent, when accessed in a multi threaded environment, like it is the case for pdsh. I filled this bugzilla, and proposed a patch that works really nice for me.
However, if rebuilding the gnome-keyring package is not an option for you, it is still possible to recover the session, and to start a new instance of an ssh-agent. The problem is that each terminal shell has an environment variable, SSH_AUTH_SOCKET, that points to the defunct ssh agent. So, the key of the hack is to symlink the control socket from the new ssh-agent instance to the socket of the crashed gkd, add the ssh keys again into the new agent, and you're done.
[bellet@monkey ~]$ env | grep SSH SSH_AUTH_SOCK=/tmp/keyring-v3d1mX/ssh SSH_ASKPASS=/usr/libexec/openssh/gnome-ssh-askpass [bellet@monkey ~]$ ssh-agent SSH_AUTH_SOCK=/tmp/ssh-TJfoGI5899/agent.5899; export SSH_AUTH_SOCK; SSH_AGENT_PID=5900; export SSH_AGENT_PID; echo Agent pid 5900; [bellet@monkey ~]$ ln -sf /tmp/ssh-TJfoGI5899/agent.5899 /tmp/keyring-v3d1mX/ssh [bellet@monkey ~]$ ssh-add Enter passphrase for /home/bellet/.ssh/id_dsa: Identity added: /home/bellet/.ssh/id_dsa (/home/bellet/.ssh/id_dsa)
Since ten years that I provide a mirror for linux distributions, I noticed that the network pressure on mirrors noticeably decreased since the beginning of this activity, although the number of packages, and the number of media carrying data greatly increased at the same time. I remember that the 100 Mbits network pipe was fully saturated for the week following the release day of popular distros. Now, the traffic is (only) multiplicated by a factor two or three for a few hours before coming back to a regular volume. Download profile also significatively evolved, from massive iso files downloads for fresh content, to a more shaped traffic related to individual packages, that come as updates of a distribution, during all its life cycle. The bulk of iso images downloads certainly shifted from client-to-server, to peer-to-peer.
I completed the migration to koji of my own personal build system to handle a set of local RPM packages for Fedora. I'm quite satisfied, as the installation instructions are rather straightforward and well documented. The possibility to use external repositories for released fedora packages is needed in my case, as my local packages come as an addition to fedora packages, just like epel needs rhl/centos, or rpmfusion needs fedora.
The necessity to merge the external repo (which is huge!) with the local one (which is small!) causes the mergerepos process to take some time to complete, and some memory resources (2Gigs for the genpkgmetadata process), so it is better to reserve enough memory+swap on the koji builders to handle this task. The kojira service, which is dedicated to this periodic activity can be disabled, and the repositories regeneration manually started when needed.
The fedora releng team provides on FedoraHosted some scripts using mash and the kojihub api, to populate a tree with the latest packages for each release of the distribution being handled in koji, to sign packages and to push them to an central location. These scripts can be reused easily in a custom setup.
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