What is the actual problem you have with a separate /var and systemd-journald? For completeness sake, which systemd version do you have?
Am Fr., 30. Apr. 2021 um 16:39 Uhr schrieb Rick Winscot <rick.wins...@gmail.com>: > > We have an embedded product that uses a minimal Linux distribution generated > via Buildroot. > > Early in the project it was decided to make the rootfs read-only... in an > effort to improve durability in environments where power fluctuations might > cause problems on the eMMC. At the same time, making logging (e.g. /var) > persistent for debugging was added to requirements. Persistent storage would > be achieved by mounting /var to a separate partition that is read-write. > > Several-hundred hours later... with many systemd-analyze reports and various > configurations tested, we have determined that managing the /var mount with > stadard services is not going to work due to tightly coupled and precisely > timed dependencies. Attempts with /etc/fstab and the systemd generator are > also unstable. > > Getting /var mounted in proximity to the initialization of > systemd-journald.service seemed illusive. > > Several days ago I found a post on Stackoverflow that tied into udev triggers > that seemed promising; resulting in the method outlined below. Initial > testing shows proper timing with all dependencies satisfied. However, the > solution feels... hackey. > > My question for anyone on the list, is the method outlined below a reasonable > solution to mounting /var early in the start-up cycle? > > Or... is there a better way? Some trimming > > > Step One: Create a systemd service that mounts /var to the specified partition > Service: /etc/systemd/system/var.service > > [Unit] > Description=service for mounting /var > DefaultDependencies=no > > [Service] > Type=oneshot > RemainAfterExit=yes > ExecStart=/bin/mount /dev/mmcblk0p6 > > > Step Two: Add a nofail mount > fstab: /etc/fstab > > /dev/root / auto rw 0 1 > /dev/mmcblk0p6 /var ext4 rw,nofail 0 0 > > > Step Three: Add a wants dependency on the mount in udev triggers (some lines > deleted for brevity) > Service: /usr/lib/systemd/system/systemd-udev-trigger.service > > [Unit] > ... > Wants=systemd-udevd.service var.service > > [Service] > ... > ExecStart=udevadm trigger --type=subsystems --action=add ; /usr/bin/udevadm > trigger > > > Finally, systemd-analyze plot shows that the mount works as desired. > > systemd-udev-trigger.service > var.service > dev-mmcblk0p6.device > var.mount > .... > systemd-remount-fs.service > systemd-journal-flush.service > local-fs-pre.target > .... > _______________________________________________ > systemd-devel mailing list > systemd-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/systemd-devel _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
