Re: [systemd-devel] systemd-timesyncd with read-only root filesystem
Hi Michael, Am 09.12.2016 um 12:43 schrieb Michael Chapman: On Fri, 9 Dec 2016, Michael Chapman wrote: [...] You will need to use the .service extension on at least the first of those links. systemd will only consider links in that directory that have valid unit names. (I'm pretty sure the intermediate link's name doesn't matter, but I wouldn't want to rely on that -- best just to use valid full unit names everywhere.) Oh, something else I thought of... I'm pretty sure it doesn't make sense having a symlink to /dev/null inside a .wants directory. Really, only the name of those links are considered. The links aren't actually dereferenced. I have to disagree on this, the name does not matter, the link target does matter (see log below, the relevant status is marked with <---). If I create a link named foo pointing to /lib/systemd/system/systemd-timesyncd.service the service is enabled and started. If I delete the link, the service is disabled and not started. Everything is fine. But it requires write access to /etc. If I create a link structure like this: /etc/systemd/system/sysinit.target.wants/systemd-timesyncd -> /mnt/writeable/systemd-timesyncd -> /lib/systemd/system/systemd-timesyncd.service the service is also started (Good). But if I then change the structure to /etc/systemd/system/sysinit.target.wants/systemd-timesyncd -> /mnt/writeable/systemd-timesyncd -> /dev/null timedatectl still says "NTP is enabled". And at this point I don't know how to proceed. Best regards, André Log: $ ssh root@192.168.16.14 Password: root@apalis-imx6:~# rm /etc/systemd/system/sysinit.target.wants/systemd-timesyncd.service root@apalis-imx6:~# reboot Connection to 192.168.16.14 closed by remote host. $ ssh root@192.168.16.14 Password: root@apalis-imx6:~# systemctl status systemd-timesyncd ● systemd-timesyncd.service - Network Time Synchronization Loaded: loaded (/lib/systemd/system/systemd-timesyncd.service; disabled; vendor preset: enabled) <--- Active: inactive (dead) Docs: man:systemd-timesyncd.service(8) root@apalis-imx6:~# timedatectl Local time: Fri 2016-12-09 13:20:46 UTC Universal time: Fri 2016-12-09 13:20:46 UTC RTC time: n/a Time zone: Universal (UTC, +) NTP enabled: no < NTP synchronized: no RTC in local TZ: no DST active: n/a root@apalis-imx6:~# cd /etc/systemd/system/sysinit.target.wants/ root@apalis-imx6:/etc/systemd/system/sysinit.target.wants# mount-rw / root@apalis-imx6:/etc/systemd/system/sysinit.target.wants# ln -s /lib/systemd/system/systemd-timesyncd.service foo root@apalis-imx6:/etc/systemd/system/sysinit.target.wants# ll foo lrwxrwxrwx1 root root45 Dec 9 13:21 foo -> /lib/systemd/system/systemd-timesyncd.service root@apalis-imx6:/etc/systemd/system/sysinit.target.wants# reboot Connection to 192.168.16.14 closed by remote host. $ ssh root@192.168.16.14 Warning: Permanently added '192.168.16.14' (ECDSA) to the list of known hosts. Password: root@apalis-imx6:~# systemctl status systemd-timesyncd ● systemd-timesyncd.service - Network Time Synchronization Loaded: loaded (/lib/systemd/system/systemd-timesyncd.service; enabled; vendor preset: enabled) <--- Active: inactive (dead) Docs: man:systemd-timesyncd.service(8) root@apalis-imx6:~# timedatectl Local time: Fri 2016-12-09 13:21:51 UTC Universal time: Fri 2016-12-09 13:21:51 UTC RTC time: n/a Time zone: Universal (UTC, +) NTP enabled: yes <--- NTP synchronized: no RTC in local TZ: no DST active: n/a root@apalis-imx6:~# ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] systemd-timesyncd with read-only root filesystem
Hi Michael, Am 09.12.2016 um 10:25 schrieb Michael Chapman: On Thu, 8 Dec 2016, André Hartmann wrote: [...] Which confuses me is the inconsistency between "systemctl status systemd.timesyncd" and "timedatectl status": # systemctl status systemd.timesyncd * systemd.timesyncd.service Loaded: not-found (Reason: No such file or directory) Active: inactive (dead) You've got a typo there -- the unit is called systemd-timesyncd.service, Your'e right, I had a typo. But after checking again, I discovered the following: cat /etc/systemd/system/sysinit.target.wants/systemd-timesyncd (empty) But systemctl status systemd-timesyncd says active (running) The link structure is as follows: /etc/systemd/system/sysinit.target.wants/systemd-timesyncd -> /mnt/writeable/systemd-timesyncd -> /dev/null So there is no inconsistency, but timesyncd is started even if it's not linked from /etc/systemd/system/sysinit.target.wants This is not what I expect. Thanks, André $ systemctl status systemd-timesyncd.service ● systemd-timesyncd.service - Network Time Synchronization Loaded: loaded (/usr/lib/systemd/system/systemd-timesyncd.service; enabled; vendor preset: disabled) ... (You can also just use "systemd-timesyncd", since systemctl will assume a .service suffix.) - Michael -- Best regards / Mit freundlichen Grüßen André Hartmann, Dipl.-Ing. (FH) Software Project Manager iseg Spezialelektronik GmbH | phone: ++49 (0)351 26996-43 Bautzner Landstr. 23| fax: ++49 (0)351 26996-21 D-01454 Radeberg / Rossendorf | web: www.iseg-hv.com Geschäftsführer / Managing director: Dr. F. Gleisberg, Dr. J. Pöthig Amtsgericht / Lower district court: Dresden HRB 16250 Ust.-Id.-Nr. / VAT-ID: DE812508942 Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet. This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and delete this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] systemd-timesyncd with read-only root filesystem
Hi Martin, thanks for keeping our dialog alive :) To sum up again what I actually want to achive: I want to use NTP after bootup by default, but in case no NTP is available, the user should be able to set the date and time by hand with timedatectl. But timedatectl refuses to do so, if "NTP is enabled". And this is my main problem: I don't know how timedatectl decides if NTP is enabled or not. The one and only thing I need, is to set the date by hand if necessary. Preferable without file write access in /etc. The configuration of most of our programs is fixed, and for the ones that need it, we have a symlink to a writeable partition. I didn't get this to work for the time configuration so far. Which confuses me is the inconsistency between "systemctl status systemd.timesyncd" and "timedatectl status": # systemctl status systemd.timesyncd * systemd.timesyncd.service Loaded: not-found (Reason: No such file or directory) Active: inactive (dead) # timedatectl status Local time: Wed 2016-12-07 16:18:06 UTC Universal time: Wed 2016-12-07 16:18:06 UTC RTC time: n/a Time zone: Universal (UTC, +) NTP enabled: yes NTP synchronized: no RTC in local TZ: no DST active: n/a I don't see an inconsistency? If timedated is not running then timedatectl can't actualy talk to it and just shows values which it can make up by itself. The inconsistence here is, that timesyncd is not running/dead (could not be started because no valid symlink to /lib/systemd/system/systemd-timesyncd exists) but timedatectl insists that NTP is enabled. Thanks for your help, André ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] systemd-timesyncd with read-only root filesystem
Hi Martin, Am 04.12.2016 um 17:48 schrieb Martin Pitt: Hello André, André Hartmann [2016-12-01 11:20 +0100]: In other words: once this symlink is valid, you cannot invalidate it by make it a dangling symlink, you have to remove it. Can somebody confirm this observation? Not a dangling one, but you should be able to make a symlink in /etc pointing to /dev/null. This is called "masking" and what "systemctl mask" does, and is sort of a stronger version of "disable" (in the sense that it will also not be started any more through Requires= and friends). My main problem is that I cannot disable NTP by setting the link to /dev/null as the root partition is read-only. And till now I don't understand how timedatectl decides "NTP enabled: yes/no". I need a possibility to disable NTP in case the user will set the date by hand (also enabling it again if the user decides otherwise). Which confuses me is the inconsistency between "systemctl status systemd.timesyncd" and "timedatectl status": # systemctl status systemd.timesyncd * systemd.timesyncd.service Loaded: not-found (Reason: No such file or directory) Active: inactive (dead) # timedatectl status Local time: Wed 2016-12-07 16:18:06 UTC Universal time: Wed 2016-12-07 16:18:06 UTC RTC time: n/a Time zone: Universal (UTC, +) NTP enabled: yes NTP synchronized: no RTC in local TZ: no DST active: n/a Any pointers here will be helpful. I assume read-only filesystems are common on embedded systems, so I assume somebody already run into this issue?! Thanks, André [1] systemd 219 +PAM -AUDIT -SELINUX +IMA -APPARMOR +SMACK +SYSVINIT +UTMP -LIBCRYPTSETUP -GCRYPT +GNUTLS +ACL +XZ -LZ4 -SECCOMP +BLKID -ELFUTILS +KMOD +IDN -- Best regards / Mit freundlichen Grüßen André Hartmann, Dipl.-Ing. (FH) Software Project Manager iseg Spezialelektronik GmbH | phone: ++49 (0)351 26996-43 Bautzner Landstr. 23| fax: ++49 (0)351 26996-21 D-01454 Radeberg / Rossendorf | web: www.iseg-hv.com Geschäftsführer / Managing director: Dr. F. Gleisberg, Dr. J. Pöthig Amtsgericht / Lower district court: Dresden HRB 16250 Ust.-Id.-Nr. / VAT-ID: DE812508942 Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet. This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and delete this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] systemd-timesyncd with read-only root filesystem
Hi Martin, Am 01.12.2016 um 10:20 schrieb Martin Pitt: Hello André, André Hartmann [2016-12-01 9:50 +0100]: So I naively created the following link structure (which works): /etc/systemd/system/sysinit.target.wants/systemd-timesyncd.service -> /mnt/writeable/systemd-timesyncd -> /lib/systemd/system/systemd-timesyncd.service But if I remove /mnt/writeable/systemd-timesyncd and reboot, the command 'timedatectl status' still reports enabled, which is unexpected. This is because systemd only really looks at the foo.wants/bar.service symlink itself -- it's actually okay for that to point into nothingness. I think this is mostly due to the fact that the actual units can be in /etc, /usr, or /run, and even move between those. The funny thing is, that foo.wants/bar.service can also point to ../baz.service, i.e. the name of the symlink does not matter. Somehow systemd seems to recognize when such a link is created and "cache" this result somewhere. In other words: once this symlink is valid, you cannot invalidate it by make it a dangling symlink, you have to remove it. Can somebody confirm this observation? And ... any other ideas how to enable/disable timesyncd? I'd like to keep as much as possible read-only, including the configurations. Thanks, Andre For example, you might have /usr/lib/systemd/system/foo.service /usr/lib/systemd/system/multi-user.target.wants/foo.service → ../foo.service and then override this with /etc/systemd/system/foo.service Then multi-user.target will still use the unit from /etc, *not* the one from /usr, even though that's where the symlink points to. In this case this is pretty obviously the correct behaviour; in your case it's admittedly confusing. I'm not entirely sure if dangling symlinks should be counted as "enabled", but this should least explain your observation. Martin ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
[systemd-devel] systemd-timesyncd with read-only root filesystem
Hi, I'm running systemd [1] on an embbeded Linux with read-only filesystem. Due to missing realtime clock, I'd like to set the clock by either NTP or by hand. To set the time by hand with 'timedatectl set-time "time"', NTP has to be disabled, but I cannot run 'timedatectl set-ntp false' due to the read-only root filesystem. If I got it right, 'timedatectl set-ntp true/false' just creates or removes the link /etc/systemd/system/sysinit.target.wants/systemd-timesyncd.service I can create/remove the link by hand too, and after rebooting 'timedatectl status' says NTP enabled or disabled. So I naively created the following link structure (which works): /etc/systemd/system/sysinit.target.wants/systemd-timesyncd.service -> /mnt/writeable/systemd-timesyncd -> /lib/systemd/system/systemd-timesyncd.service But if I remove /mnt/writeable/systemd-timesyncd and reboot, the command 'timedatectl status' still reports enabled, which is unexpected. Do you have any hints or recommendations on this? Thanks and best regards, Andre [1] systemd 219 +PAM -AUDIT -SELINUX +IMA -APPARMOR +SMACK +SYSVINIT +UTMP -LIBCRYPTSETUP -GCRYPT +GNUTLS +ACL +XZ -LZ4 -SECCOMP +BLKID -ELFUTILS +KMOD +IDN ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
