Package: general, apt Severity: normal Today I ran "aptitude update ; aptitude dist-upgrade" on my virtual machine that provides some web applications to the clients. There were 126 updated packages (accumulated since 2012-06-18). The upgrade and the following kexec-based reboot went well, except for one thing: it took too long between stopping and starting again apache and mysql.
A technology exists that can keep downtime to a minimum. It is called "btrfs snapshots", see below for the details. After Wheezy, Debian should support it natively in installer, dpkg and apt/aptitude. 1) The installer should be able to install the system to a btrfs subvolume (except /home and /var, which should be on separate subvolumes). 2) On such system, dpkg and apt/aptitude, if requested by the user and/or by default, should make a writeable snapshot of the root subvolume, mount it to some temporary location, chroot into it and perform the upgrade there. During this process, the main system will, of course, continue to work. 3) Then a kexec-based reboot should happen, using the new subvolume as the root filesystem. A kexec-based reboot is currently faster than a two-week dist-upgrade of the testing distribution, and thus it should be good for minimizing the downtime. Besides, the kernel is upgraded often in the testing distribution, thus a reboot is needed anyway. Maybe this procedure is also doable with LVM snapshots. Also note that this is different from the "offline updates" proposal from Lennart Poettering (that essentially involves running the current dist-upgrade between two reboots) and has different goals. His goal is to ensure consistency during and after the upgrade, my goal is to minimize downtime. -- System Information: Debian Release: wheezy/sid APT prefers testing APT policy: (500, 'testing') Architecture: amd64 (x86_64) Kernel: Linux 3.2.0-2-amd64 (SMP w/1 CPU core) Locale: LANG=ru_RU.UTF-8, LC_CTYPE=ru_RU.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash -- Alexander E. Patrakov -- To UNSUBSCRIBE, email to debian-devel-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/can_lgv2gkvhsxmtkb6jsm6egep_nn_od3pm4gk-7jwax9g7...@mail.gmail.com
