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Evy Bongers's questions

Martin Hope
Evy Bongers
Asked: 2021-07-05 22:47:42 +0800 CST
  • 3

A while ago I set up a systemd service to run after network comes online per the documentation. This is the unit file:

[Unit]
Description=Refresh Pacman mirrorlist with Reflector.
Documentation=https://wiki.archlinux.org/index.php/Reflector
Wants=network-online.target
After=network-online.target nss-lookup.target

[Service]
Type=oneshot
ExecStart=/usr/bin/reflector @/etc/xdg/reflector/reflector.conf
CacheDirectory=reflector
CapabilityBoundingSet=~CAP_SETUID CAP_SETGID CAP_SETPCAP CAP_SYS_ADMIN CAP_SYS_PTRACE CAP_CHOWN CAP_FSETID CAP_SETFCAP CAP_DAC_OVERRIDE CAP_DAC_READ_SEARCH CAP_FOWNER CAP_IPC_OWNER CAP_NET_ADMIN CAP_SYS_TIME CAP_AUDIT_CONTROL CAP_AUDIT_READ CAP_AUDIT_WRITE CAP_KILL CAP_NET_BIND_SERVICE CAP_NET_BROADCAST CAP_NET_RAW CAP_SYS_NICE CAP_SYS_RESOURCE CAP_MAC_ADMIN CAP_MAC_OVERRIDE CAP_SYS_BOOT CAP_LINUX_IMMUTABLE CAP_IPC_LOCK CAP_SYS_CHROOT CAP_BLOCK_SUSPEND CAP_LEASE CAP_SYS_PACCT CAP_SYS_TTY_CONFIG CAP_WAKE_ALARM
Environment=XDG_CACHE_HOME=/var/cache/reflector
LockPersonality=true
MemoryDenyWriteExecute=true
NoNewPrivileges=true
PrivateDevices=true
PrivateTmp=true
PrivateUsers=true
ProtectClock=true
ProtectControlGroups=true
ProtectHome=true
ProtectHostname=true
ProtectKernelTunables=true
ProtectKernelLogs=true
ProtectKernelModules=true
ProtectSystem=strict
ReadOnlyPaths=/etc/xdg/reflector/reflector.conf
ReadWritePaths=/etc/pacman.d/mirrorlist
RemoveIPC=true
RestrictAddressFamilies=~AF_AX25 AF_IPX AF_APPLETALK AF_X25 AF_DECnet AF_KEY AF_NETLINK AF_PACKET AF_RDS AF_PPPOX AF_LLC AF_IB AF_MPLS AF_CAN AF_TIPC AF_BLUETOOTH AF_ALG AF_VSOCK AF_KCM AF_UNIX AF_XDP
RestrictNamespaces=true
RestrictRealtime=true
RestrictSUIDSGID=true
SystemCallArchitectures=native
SystemCallFilter=@system-service
SystemCallFilter=~@resources @privileged
UMask=177

[Install]
WantedBy=multi-user.target

Per the documentation, the service should already be set up correctly to wait for network connectivity to be established (i.e.: I'm logged in, NetworkManager has connected to WiFi and the system has been assigned an IP).

network-online.target is a target that actively waits until the nework is "up", where the definition of "up" is defined by the network management software. Usually it indicates a configured, routable IP address of some kind. Its primary purpose is to actively delay activation of services until the network is set up.

I've also made sure that NetworkManager-wait-online.service is enabled.

$ systemctl is-enabled NetworkManager-wait-online.service systemd-networkd-wait-online.service
enabled
disabled

Instead of the service waiting to start until an internet connection has been established, I see an error on the system console almost as soon as I see my login prompt.

Jul 05 07:40:02 gadget systemd[1]: Starting Refresh Pacman mirrorlist with Reflector....
Jul 05 07:40:03 gadget reflector[564]: error: failed to retrieve mirrorstatus data: URLError: <urlopen error [Errno -3] Temporary failure in name resolution>
Jul 05 07:40:03 gadget systemd[1]: reflector.service: Main process exited, code=exited, status=1/FAILURE
Jul 05 07:40:03 gadget systemd[1]: reflector.service: Failed with result 'exit-code'.
Jul 05 07:40:03 gadget systemd[1]: Failed to start Refresh Pacman mirrorlist with Reflector..

Since it should wait for network to be online and DNS to be available, I also checked the status of NetworkManager-wait-online.service, network-online.target and nss-lookup.target:

$ systemctl status NetworkManager-wait-online.service
● NetworkManager-wait-online.service - Network Manager Wait Online
     Loaded: loaded (/usr/lib/systemd/system/NetworkManager-wait-online.service; enabled; vendor preset: disabled)
     Active: active (exited) since Mon 2021-07-05 07:40:02 CEST; 44min ago
       Docs: man:nm-online(1)
   Main PID: 544 (code=exited, status=0/SUCCESS)
      Tasks: 0 (limit: 38321)
     Memory: 0B
        CPU: 0
     CGroup: /system.slice/NetworkManager-wait-online.service

Jul 05 07:40:02 gadget systemd[1]: Starting Network Manager Wait Online...
Jul 05 07:40:02 gadget systemd[1]: Finished Network Manager Wait Online.
$ systemctl status network-online.target
● network-online.target - Network is Online
     Loaded: loaded (/usr/lib/systemd/system/network-online.target; static)
     Active: active since Mon 2021-07-05 07:40:02 CEST; 1h 5min ago
       Docs: man:systemd.special(7)
             https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget

Jul 05 07:40:02 gadget systemd[1]: Reached target Network is Online.
$ systemctl status nss-lookup.target
○ nss-lookup.target - Host and Network Name Lookups
     Loaded: loaded (/usr/lib/systemd/system/nss-lookup.target; static)
     Active: inactive (dead)
       Docs: man:systemd.special(7)

It strikes me as odd that NetworkManager-wait-online.service reports finished right after starting. Is there something else I need to configure? Is this a bug in NetworkManager and/or nm-online?

I've looked for similar topics and found these questions, but they don't answer my issue:

linux systemd systemd-service
Martin Hope
Evy Bongers
Asked: 2019-05-18 01:06:47 +0800 CST
  • 0

Recently the backup script I've been using for years has started to give me trouble. The part that's problematic boils down to this:

for DIR in "${BACKUP_DIRS[@]}"; do
    rsync --acls --archive --delete \
        --link-dest=${DIR} \
        --stats \
        --verbose \
        --rsh="ssh -o BatchMode=yes -i ${KEY}" \
        "${USER}"@${HOST}:"${DIR}" "${BACKUP_DIR}/"
done

Now the problem I have is that on the first (and only the first) directory listed in ${BACKUP_DIRS[@]}, rsync exits with an error:

ssh: Could not resolve hostname <host>: Name or service not known
rsync: connection unexpectedly closed (0 bytes received so far) [Receiver]
rsync error: unexplained error (code 255) at io.c(226) [Receiver=3.1.3]
An error occurred during backup of <dir>.

Any clues on how to resolve this are very much appreciated.

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