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What I also don’t get: why the hell would do I care which NTP implementation is used in most cases. What I do care about is that it’s running and working. syste

What I also don’t get: why the hell would do I care which NTP implementation is used in most cases. What I do care about is that it’s running and working. systemd has a good init system and a decent set of other services. Could things be improved? Sure. But honestly as long as when I boot my Debian-derived distro it works as expected why am I going yo go digging into how it works? What can I possibly gain by switching which DHCP client or which NTP daemon I’m using?

throw0101a 5y ago
> What I also don’t get: why the hell would do I care which NTP implementation is used in most cases. Because some implementations have time jump while others have it slew it slowly. On boot-up a jump may be fine to get with ± some number of milliseconds, but once the system is running, there are situations where jumps could be a problem (especially in the negative direction, where a moment is "repeated"). > But honestly as long as when I boot my Debian-derived distro it works as expected why am I going yo go digging into how it works? What can I possibly gain by switching which DHCP client or which NTP daemon I’m using? Because as a sysadmin it is your job to understand how a system works. There should be very little "magic" happening. Sure there are many times where things Just Working™ is fine (it's why I run a Mac at home), but many others where you should understand why things are working the way they are.
- Denvercoder9 5y ago
  > Because as a sysadmin it is your job to understand how a system works. No, as a sysadmin your job is to deliver a working system. To do that it usually helps to understand how the system works, but it's not a necessity. As long as something keeps working, and you're equipped to go digging if and when it's necessary, it's fine to not understand or know how something works.
  - totony 5y ago
    >As long as something keeps working, and you're equipped to go digging if and when it's necessary, it's fine to not understand or know how something works How do you know it's working if you don't understand it? What's preventing some admin socket to be activated, is the firewall good, etc
  - someguydave 5y ago
    you can ride and breed horses without understanding horse physiology or DNA. when you need to fix a broken or lame horse or breed a better horse, knowing how it works helps alot presumably most sys admins are more akin to vets than riders
- IgorPartola 5y ago
  I am a sysadmin for some systems. I am merely a user for others. Servers that run my projects? Sure I will dig into what’s up. My Raspberry Pi running Raspbian so I can run my 3D printer off it? I’m a user.
cesarb 5y ago
> What I also don’t get: why the hell would do I care which NTP implementation is used in most cases. What I do care about is that it’s running and working. You should care whether it's SNTP (which only slews and/or steps the clock periodically) or full NTP (which also adjusts the clock frequency, so once it's synchronized, no further slew and/or step is needed). Full NTP is better. Looking quickly at the manual pages for systemd-timesyncd and systemd-timedated, I can see that systemd-timesyncd is just SNTP, so a full NTP implementation like chrony or ntpsec should be preferred. From what I can see, if you have chrony installed and configured correctly, systemd's "timedatectl set-ntp true" (enable NTP) will prefer to enable chrony instead of systemd-timesyncd (it goes through systemd-timedated which looks at /usr/lib/systemd/ntp-units.d/, where chrony is usually listed first). (Also, there's some difference between chrony and ntpsec; AFAIK, chrony is much better when you have an intermittent network connection.)
yosamino 5y ago
> What can I possibly gain by switching which DHCP client Yesterday I switched to systemd-networkd on debian to gain the feature of having the hostname be set via DHCP and not have to write a script myself. In the process I pulled in a javascript dependency via policykit, which is giving me pause and I am re-evaluating if my approach is correct here. But for this feature I had to switch DHCP server and client. TBF it's not something that comes up all the time, but it sure is something I thought was more commonly implemented.
- xyzzy_plugh 5y ago
  > In the process I pulled in a javascript dependency via policykit, which is giving me pause and I am re-evaluating if my approach is correct here. To be fair, policykit is great. It solves a real problem (namely is this user allowed to peform this action, which traditional POSIX permissions do not solve in a portably) in a very sane way that is totally optional to opt in to. Should polkit use a different, turing complete language than JavaScript? I don't know, probably, but it's not an awful choice. There is definitely more developer literacy for JS than, say, Lua or some other bespoke monstrosity they could've picked instead.
  - someperson 5y ago
    Doesn't POSIX and Linux Standard Base already mandate certain scripting languages to be preinstalled, such as Python?
    - thristian 5y ago
      I've heard a rumour that POSIX mandates that Perl be installed, although I haven't been able to substantiate it. POSIX-described Turing-complete interpreters include at leat the Bourne shell, awk, and sed, none of which you probably want to use for implementing a security policy. Apparently LSB 5.0 mandates[1] both Perl (5.8) and Python (2.4), but that won't pacify anyone with an axe to grind about applications making Linux-specific assumptions. [1]: https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Languages/LSB-Languages/book1.html https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Languages...
floatboth 5y ago
I care about which NTP implementation is used because OpenNTPD supports getting time constraints from TLS servers. Which.. no, I absolutely do not actually worry about NTP servers intentionally feeding my laptop the wrong time, but this is just a feature that sounds too cool to ignore. How can I not go out of my way to have that going on?? Sometimes I kinda envy people who don't have this shiny-tech-obsession and are satisfied with things just working :)
- IgorPartola 5y ago
  Oh don’t get me wrong I customize things. I have just moved on from customizing parts of a Linux distro. At some point I want to customize things that make more of an impact on the real world.
donmcronald 5y ago
> But honestly as long as when I boot my Debian-derived distro it works as expected why am I going yo go digging into how it works? My (least) favorite SystemD gotcha I discovered recently is the way it's taken over 'fstab' in some distros. I think Debian is one of them. When you edit 'fstab', you need to run 'systemctl daemon-reload'. Fine. Whatever. I don't have a huge problem with that. However, when you try to boot after a disk has been removed from the system, it won't. Instead it drops to a recovery console, BUT if you use a distro without a 'root' password, it can't drop into the recovery console and you're screwed. The default setup on a lot of Linux distros won't boot if you remove a non-system disk. I like SystemD more than the old init system(s), but there are some really, really dumb decisions that have been made along the way.
- jasonjayr 5y ago
  Yep. Hit that one too. Learned the hard way the need for the 'nofail' flag in 'fs_mntops' field, which was undocumented in the man page in the early versions ...
- gigatexal 5y ago
  Ok that’s a bit much. Why is SystemD encroaching on the fstab??
  - jcelerier 5y ago
    Because systemd services can depend on mount points or cause mountpoints to come up dynamically, in a way that pure fstab does not support, e.g. for containers. So (as far as I understand) fstab is now simply an input to the actual mount system.
  - Denvercoder9 5y ago
    It's not encroaching on fstab, it's using it as input during boot, because mounting is intimately coupled with service ordering. Think about services that reside on a network filesystem: the network has to be up to mount the filesystem, but the network in turn can require arbitrary services to run, which can require other local filesystems to be mounted. You can't get configurations like these to work without coupling mounting and service ordering. It's fundamentally not that different from sysvinit, with its various init scripts that mounted filesystems according to the fstab.
djrogers 5y ago
> why the hell would do I care which NTP implementation is used Allow me to introduce you to BSD users. (I don’t get it either).

throw0101a 5y ago

> What I also don’t get: why the hell would do I care which NTP implementation is used in most cases. Because some implementations have time jump while others have it slew it slowly. On boot-up a jump may be fine to get with ± some number of milliseconds, but once the system is running, there are situations where jumps could be a problem (especially in the negative direction, where a moment is "repeated"). > But honestly as long as when I boot my Debian-derived distro it works as expected why am I going yo go digging into how it works? What can I possibly gain by switching which DHCP client or which NTP daemon I’m using? Because as a sysadmin it is your job to understand how a system works. There should be very little "magic" happening. Sure there are many times where things Just Working™ is fine (it's why I run a Mac at home), but many others where you should understand why things are working the way they are.

Denvercoder9 5y ago
> Because as a sysadmin it is your job to understand how a system works. No, as a sysadmin your job is to deliver a working system. To do that it usually helps to understand how the system works, but it's not a necessity. As long as something keeps working, and you're equipped to go digging if and when it's necessary, it's fine to not understand or know how something works.
- totony 5y ago
  >As long as something keeps working, and you're equipped to go digging if and when it's necessary, it's fine to not understand or know how something works How do you know it's working if you don't understand it? What's preventing some admin socket to be activated, is the firewall good, etc
- someguydave 5y ago
  you can ride and breed horses without understanding horse physiology or DNA. when you need to fix a broken or lame horse or breed a better horse, knowing how it works helps alot presumably most sys admins are more akin to vets than riders
IgorPartola 5y ago
I am a sysadmin for some systems. I am merely a user for others. Servers that run my projects? Sure I will dig into what’s up. My Raspberry Pi running Raspbian so I can run my 3D printer off it? I’m a user.

cesarb 5y ago

> What I also don’t get: why the hell would do I care which NTP implementation is used in most cases. What I do care about is that it’s running and working. You should care whether it's SNTP (which only slews and/or steps the clock periodically) or full NTP (which also adjusts the clock frequency, so once it's synchronized, no further slew and/or step is needed). Full NTP is better. Looking quickly at the manual pages for systemd-timesyncd and systemd-timedated, I can see that systemd-timesyncd is just SNTP, so a full NTP implementation like chrony or ntpsec should be preferred. From what I can see, if you have chrony installed and configured correctly, systemd's "timedatectl set-ntp true" (enable NTP) will prefer to enable chrony instead of systemd-timesyncd (it goes through systemd-timedated which looks at /usr/lib/systemd/ntp-units.d/, where chrony is usually listed first). (Also, there's some difference between chrony and ntpsec; AFAIK, chrony is much better when you have an intermittent network connection.)

yosamino 5y ago

> What can I possibly gain by switching which DHCP client Yesterday I switched to systemd-networkd on debian to gain the feature of having the hostname be set via DHCP and not have to write a script myself. In the process I pulled in a javascript dependency via policykit, which is giving me pause and I am re-evaluating if my approach is correct here. But for this feature I had to switch DHCP server and client. TBF it's not something that comes up all the time, but it sure is something I thought was more commonly implemented.

xyzzy_plugh 5y ago
> In the process I pulled in a javascript dependency via policykit, which is giving me pause and I am re-evaluating if my approach is correct here. To be fair, policykit is great. It solves a real problem (namely is this user allowed to peform this action, which traditional POSIX permissions do not solve in a portably) in a very sane way that is totally optional to opt in to. Should polkit use a different, turing complete language than JavaScript? I don't know, probably, but it's not an awful choice. There is definitely more developer literacy for JS than, say, Lua or some other bespoke monstrosity they could've picked instead.
- someperson 5y ago
  Doesn't POSIX and Linux Standard Base already mandate certain scripting languages to be preinstalled, such as Python?
  - thristian 5y ago
    I've heard a rumour that POSIX mandates that Perl be installed, although I haven't been able to substantiate it. POSIX-described Turing-complete interpreters include at leat the Bourne shell, awk, and sed, none of which you probably want to use for implementing a security policy. Apparently LSB 5.0 mandates[1] both Perl (5.8) and Python (2.4), but that won't pacify anyone with an axe to grind about applications making Linux-specific assumptions. [1]: https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Languages/LSB-Languages/book1.html https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Languages...

floatboth 5y ago

I care about which NTP implementation is used because OpenNTPD supports getting time constraints from TLS servers. Which.. no, I absolutely do not actually worry about NTP servers intentionally feeding my laptop the wrong time, but this is just a feature that sounds too cool to ignore. How can I not go out of my way to have that going on?? Sometimes I kinda envy people who don't have this shiny-tech-obsession and are satisfied with things just working :)

IgorPartola 5y ago
Oh don’t get me wrong I customize things. I have just moved on from customizing parts of a Linux distro. At some point I want to customize things that make more of an impact on the real world.

donmcronald 5y ago

> But honestly as long as when I boot my Debian-derived distro it works as expected why am I going yo go digging into how it works? My (least) favorite SystemD gotcha I discovered recently is the way it's taken over 'fstab' in some distros. I think Debian is one of them. When you edit 'fstab', you need to run 'systemctl daemon-reload'. Fine. Whatever. I don't have a huge problem with that. However, when you try to boot after a disk has been removed from the system, it won't. Instead it drops to a recovery console, BUT if you use a distro without a 'root' password, it can't drop into the recovery console and you're screwed. The default setup on a lot of Linux distros won't boot if you remove a non-system disk. I like SystemD more than the old init system(s), but there are some really, really dumb decisions that have been made along the way.

jasonjayr 5y ago
Yep. Hit that one too. Learned the hard way the need for the 'nofail' flag in 'fs_mntops' field, which was undocumented in the man page in the early versions ...
gigatexal 5y ago
Ok that’s a bit much. Why is SystemD encroaching on the fstab??
- jcelerier 5y ago
  Because systemd services can depend on mount points or cause mountpoints to come up dynamically, in a way that pure fstab does not support, e.g. for containers. So (as far as I understand) fstab is now simply an input to the actual mount system.
- Denvercoder9 5y ago
  It's not encroaching on fstab, it's using it as input during boot, because mounting is intimately coupled with service ordering. Think about services that reside on a network filesystem: the network has to be up to mount the filesystem, but the network in turn can require arbitrary services to run, which can require other local filesystems to be mounted. You can't get configurations like these to work without coupling mounting and service ordering. It's fundamentally not that different from sysvinit, with its various init scripts that mounted filesystems according to the fstab.

djrogers 5y ago

> why the hell would do I care which NTP implementation is used Allow me to introduce you to BSD users. (I don’t get it either).