I've been struggling to make sense of something, so would appreciate some help.
I am mounting a remote NFS drive onto my Debian system with the following fstab entry which uses the systemd automounter, and is set to auto-unmount after 120 seconds of inactivity:
192.168.0.67:/mnt/SSD_240GB/backups/TIG_backups /mnt/nfs/SSD_240GB/backups/TIG_backups nfs auto,_netdev,bg,soft,x-systemd.automount,x-systemd.idle-timeout=120,timeo=14,nofail,noatime,nolock,tcp,actimeo=1800 0 0 Now on this Debian host system I am running a docker container (Telegraf), to monitor some metrics of the Debian host. To facilitate this, I am bind-mounting the host filesystem and proc directory (as recommended here in the docs), as well as bind-mounting the NFS drive. The docker run command looks like this:
docker run -d \ --name telegraf_container \ --user 1001:1001 \ --network docker_monitoring_network \ --mount type=bind,source=/,destination=/hostfs \ --mount type=bind,source=/mnt/nfs/SSD_240GB/backups/TIG_backups/telegraf_backups,destination=/mnt/nfs/SSD_240GB/backups/TIG_backups/telegraf_backups \ -e HOST_MOUNT_PREFIX=/hostfs \ -e HOST_PROC=/hostfs/proc \ telegraf:latest I am using the Telegraf Disk Input plugin because I want to gather disk usage metrics once every hour for the NFS drive (used, free, total). The problem is that the disk is unmounted automatically 120s after system boot as expected, but it is never remounted.
I would expect the telegraf container to trigger an automount every hour. The reason I expect this is because the container is essentially running a .go program (as seen here in the source code) which is querying the filesystem. I believe under the hood it is calling some .go libraries (here and here), which are essentially calling statfs(). I was under the impression that statfs() should trigger a systemd automount.
Here in the Debian host's logs, I can see the NFS drive mounting correctly at boot up, and then unmounting after a couple of minutes automatically (but then it never remounts):
root@docker-debian:/home/monitoring/docker_files/scripts# journalctl -u mnt-nfs-SSD_240GB-backups-TIG_backups.automount -b Jun 05 13:54:12 docker-debian systemd[1]: Set up automount mnt-nfs-SSD_240GB-backups-TIG_backups.automount. Jun 05 13:54:18 docker-debian systemd[1]: mnt-nfs-SSD_240GB-backups-TIG_backups.automount: Got automount request for /mnt/nfs/SSD_240GB/backups/TIG_backups, triggered by 893 (runc:[2:INIT]) root@docker-debian:/home/monitoring/docker_files/scripts# journalctl -u mnt-nfs-SSD_240GB-backups-TIG_backups.mount -b Jun 05 13:54:18 docker-debian systemd[1]: Mounting mnt-nfs-SSD_240GB-backups-TIG_backups.mount - /mnt/nfs/SSD_240GB/backups/TIG_backups... Jun 05 13:54:18 docker-debian systemd[1]: Mounted mnt-nfs-SSD_240GB-backups-TIG_backups.mount - /mnt/nfs/SSD_240GB/backups/TIG_backups. Jun 05 13:57:39 docker-debian systemd[1]: Unmounting mnt-nfs-SSD_240GB-backups-TIG_backups.mount - /mnt/nfs/SSD_240GB/backups/TIG_backups... Jun 05 13:57:39 docker-debian systemd[1]: mnt-nfs-SSD_240GB-backups-TIG_backups.mount: Deactivated successfully. Jun 05 13:57:39 docker-debian systemd[1]: Unmounted mnt-nfs-SSD_240GB-backups-TIG_backups.mount - /mnt/nfs/SSD_240GB/backups/TIG_backups. After the drive has auto-unmounted, it is missing from the host as expected:
monitoring@docker-debian:/$ df Filesystem 1K-blocks Used Available Use% Mounted on udev 983908 0 983908 0% /dev tmpfs 201420 816 200604 1% /run /dev/sda1 15421320 4779404 9836748 33% / tmpfs 1007084 0 1007084 0% /dev/shm tmpfs 5120 0 5120 0% /run/lock tmpfs 201416 0 201416 0% /run/user/1001 But it is present in the container:
monitoring@docker-debian:/$ docker exec -it telegraf_container df Filesystem 1K-blocks Used Available Use% Mounted on overlay 15421320 4779404 9836748 33% / tmpfs 65536 0 65536 0% /dev shm 65536 0 65536 0% /dev/shm /dev/sda1 15421320 4779404 9836748 33% /hostfs udev 983908 0 983908 0% /hostfs/dev tmpfs 1007084 0 1007084 0% /hostfs/dev/shm tmpfs 201420 820 200600 1% /hostfs/run tmpfs 5120 0 5120 0% /hostfs/run/lock 192.168.0.67:/mnt/SSD_240GB/backups/TIG_backups/telegraf_backups 229608448 42336256 175535104 20% /mnt/nfs/SSD_240GB/backups/TIG_backups/telegraf_backups tmpfs 1007084 0 1007084 0% /proc/acpi tmpfs 1007084 0 1007084 0% /sys/firmware tmpfs 201416 0 201416 0% /hostfs/run/user/1001 In case it's relevant, the Telegraf config is here:
# GLOBAL SETTINGS [agent] hostname = "docker-debian" flush_interval = "60m" interval = "60m" # COLLECT DISK USAGE OF THIS VM [[inputs.disk]] mount_points = ["/", "/mnt/nfs/SSD_240GB/backups/TIG_backups"] # Only these will be checked fieldpass = [ "free", "total", "used", "used_percent" ] ignore_fs = ["tmpfs", "devtmpfs", "devfs", "iso9660", "overlay", "aufs", "squashfs"] # VIEW COLLECTED METRICS [[outputs.file]] files = ["stdout"] Why is the container not triggering an automount, which leads to it not being able to collect the metrics on the drive?