Re: [systemd-devel] minimal required units
В Thu, 12 Mar 2015 13:49:38 -0700 aaron_wri...@selinc.com пишет: Andrei Borzenkov arvidj...@gmail.com wrote on 03/12/2015 12:18:15 PM: From: Andrei Borzenkov arvidj...@gmail.com To: aaron_wri...@selinc.com Cc: systemd-devel@lists.freedesktop.org Date: 03/12/2015 12:18 PM Subject: Re: [systemd-devel] minimal required units В Thu, 12 Mar 2015 11:09:57 -0700 aaron_wri...@selinc.com пишет: I feel like there needs to be a list of required units to get base functionality out of systemd. So that embedded guys like me can build up a system from scratch, instead of starting from full blown desktop support and guessing at what can be taken out. sysinit.target is supposed to get you minimal working system (more or less what you got with single user in the past). It could be considered as starting point. Most embedded systems I have seen were running something very close to single user anyway. Right now, I'm starting with the basic.target. Gets me a few more features than sysinit.target, such as timers, which I feel I can use in my product to replace cron. My question is mainly about whether the list of actual required units is known, or if it is something that requires investigation (digging through a bunch of code). Did you see bootup(7)? Yes, I've read that a few times, and I love the diagram. It seems to suggest to me that I can use basic.target as a good synchronization point, and then add my units after that, which makes sense to me. If I include at least all of the units leading up to basic.target, would that cover the units required by systemd? systemd does not really require anything. Really. *You* (or your system) require something to be started during boot and only you know what should be started. You can use single service that calls /etc/rc as starting point and split it up step by step. Units shipped with systemd help to organize system startup in logical steps and provide common hooks to plug your own extensions into. Removing common hooks won't buy you anything but will make system less flexible and harder to troubleshoot. Though, that would include lots of things I don't need, such as cryptsetup.target, swap.target, mqueue, configfs, debugfs, etc. If you do not use them, do not include them. But cryptsetup.target or swap.target will not even appear if you do not have /etc/crypttab or swaps and others you mention check whether they can be started. I'm concerned because I left out local-fs.target to begin with, as I don't need systemd to mount anything, but that seemed to cause systemd to unmount everything other than / and the kernel file systems. Sorry, that does not fit. Either you do not need to mount anything or systemd unmount everything. What was there to unmount if you did not mount anything in the first place? So I got bit by there not being any documentation that says, local-fs.target is Required. Unless, I'm missing something. It is very hard to answer without seeing more details. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] minimal required units
Andrei Borzenkov arvidj...@gmail.com wrote on 03/11/2015 08:47:43 PM: From: Andrei Borzenkov arvidj...@gmail.com To: aaron_wri...@selinc.com Cc: systemd-devel@lists.freedesktop.org Date: 03/11/2015 08:47 PM Subject: Re: [systemd-devel] minimal required units В Wed, 11 Mar 2015 12:02:29 -0700 aaron_wri...@selinc.com пишет: I'm trying to make an embedded device, and I would like to start with the minimal setup as possible. Are there some units that are required by systemd? I ask because systemd is complaining about a missing rescue.target unit, When does it do it? It was doing this because my default unit was not set correctly. But that isn't really the question. The question is, what units are required by systemd? How can I figure that out? It seems like rescue.target, local-fs.target, and local-fs-pre.target are required, but I've only discovered that after trial and error. I know the systemd.special man page lists a ton of special units, but it seems that not all of them are required. Right? Well, which ones are? I feel like I need to look through the code to see when a hardcoded unit is referenced, like rescue.target was, that I don't know about. My device doesn't have many of the same requirements of a full desktop or server Linux, so I'm trying to strip out things from systemd, unit wise, that I don't want or need. I've customized sysinit.target and basic.target to just reference the units I want. And that seems to be going smooth, but it appears there are other units, that I didn't know about that are required, but that aren't documented as such (that I could find). This scares me a bit. but I don't list rescue.target as a dependency of any other unit. However, grep tells me that /usr/lib/systemd/systemd contains the rescue.target string, which worries me. Is there a list of all the units that are required, even though no other unit lists them? ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] minimal required units
Sorry for the noise, I have now read that you have already seen it. On Thu, Mar 12, 2015 at 5:32 PM, Peter Sztan sztan...@gmail.com wrote: man 7 systemd.special On Thu, Mar 12, 2015 at 4:41 PM, aaron_wri...@selinc.com wrote: Andrei Borzenkov arvidj...@gmail.com wrote on 03/11/2015 08:47:43 PM: From: Andrei Borzenkov arvidj...@gmail.com To: aaron_wri...@selinc.com Cc: systemd-devel@lists.freedesktop.org Date: 03/11/2015 08:47 PM Subject: Re: [systemd-devel] minimal required units В Wed, 11 Mar 2015 12:02:29 -0700 aaron_wri...@selinc.com пишет: I'm trying to make an embedded device, and I would like to start with the minimal setup as possible. Are there some units that are required by systemd? I ask because systemd is complaining about a missing rescue.target unit, When does it do it? It was doing this because my default unit was not set correctly. But that isn't really the question. The question is, what units are required by systemd? How can I figure that out? It seems like rescue.target, local-fs.target, and local-fs-pre.target are required, but I've only discovered that after trial and error. I know the systemd.special man page lists a ton of special units, but it seems that not all of them are required. Right? Well, which ones are? I feel like I need to look through the code to see when a hardcoded unit is referenced, like rescue.target was, that I don't know about. My device doesn't have many of the same requirements of a full desktop or server Linux, so I'm trying to strip out things from systemd, unit wise, that I don't want or need. I've customized sysinit.target and basic.target to just reference the units I want. And that seems to be going smooth, but it appears there are other units, that I didn't know about that are required, but that aren't documented as such (that I could find). This scares me a bit. but I don't list rescue.target as a dependency of any other unit. However, grep tells me that /usr/lib/systemd/systemd contains the rescue.target string, which worries me. Is there a list of all the units that are required, even though no other unit lists them? ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] minimal required units
В Thu, 12 Mar 2015 09:42:25 -0700 aaron_wri...@selinc.com пишет: Peter Sztan sztan...@gmail.com wrote on 03/12/2015 09:33:38 AM: From: Peter Sztan sztan...@gmail.com To: aaron_wri...@selinc.com Cc: systemd Mailing List systemd-devel@lists.freedesktop.org Date: 03/12/2015 09:33 AM Subject: Re: [systemd-devel] minimal required units Sorry for the noise, I have now read that you have already seen it. Just for illustration purposes, here are few units listed in systemd.special, that I don't feel like I need, but which I'm left wondering if systemd needs them: cryptsetup.target display-manager.service getty.target graphical.target hibernate.target hybrid-sleep.target halt.target initrd-fs.target kbrequest.target multi-user.target network-online.target poweroff.target remote-fs.target initrd-root-fs.target runlevel*.target sigpwr.target sleep.target suspend.target swap.target targets serve as common reference for collection of other units (services). They do not do anything by themselves, there is absolutely no reason to remove them. Some of them (at least those mentioned in systemd.special) do have special meaning and removing them will actually break functionality. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] minimal required units
Peter Sztan sztan...@gmail.com wrote on 03/12/2015 09:33:38 AM: From: Peter Sztan sztan...@gmail.com To: aaron_wri...@selinc.com Cc: systemd Mailing List systemd-devel@lists.freedesktop.org Date: 03/12/2015 09:33 AM Subject: Re: [systemd-devel] minimal required units Sorry for the noise, I have now read that you have already seen it. Just for illustration purposes, here are few units listed in systemd.special, that I don't feel like I need, but which I'm left wondering if systemd needs them: cryptsetup.target display-manager.service getty.target graphical.target hibernate.target hybrid-sleep.target halt.target initrd-fs.target kbrequest.target multi-user.target network-online.target poweroff.target remote-fs.target initrd-root-fs.target runlevel*.target sigpwr.target sleep.target suspend.target swap.target (and so on) I can't tell from systemd.special if these are required or not. On Thu, Mar 12, 2015 at 5:32 PM, Peter Sztan sztan...@gmail.com wrote: man 7 systemd.special On Thu, Mar 12, 2015 at 4:41 PM, aaron_wri...@selinc.com wrote: Andrei Borzenkov arvidj...@gmail.com wrote on 03/11/2015 08:47:43 PM: From: Andrei Borzenkov arvidj...@gmail.com To: aaron_wri...@selinc.com Cc: systemd-devel@lists.freedesktop.org Date: 03/11/2015 08:47 PM Subject: Re: [systemd-devel] minimal required units В Wed, 11 Mar 2015 12:02:29 -0700 aaron_wri...@selinc.com пишет: I'm trying to make an embedded device, and I would like to start with the minimal setup as possible. Are there some units that are required by systemd? I ask because systemd is complaining about a missing rescue.target unit, When does it do it? It was doing this because my default unit was not set correctly. But that isn't really the question. The question is, what units are required by systemd? How can I figure that out? It seems like rescue.target, local-fs.target, and local-fs-pre.target are required, but I've only discovered that after trial and error. I know the systemd.special man page lists a ton of special units, but it seems that not all of them are required. Right? Well, which ones are? I feel like I need to look through the code to see when a hardcoded unit is referenced, like rescue.target was, that I don't know about. My device doesn't have many of the same requirements of a full desktop or server Linux, so I'm trying to strip out things from systemd, unit wise, that I don't want or need. I've customized sysinit.target and basic.target to just reference the units I want. And that seems to be going smooth, but it appears there are other units, that I didn't know about that are required, but that aren't documented as such (that I could find). This scares me a bit. but I don't list rescue.target as a dependency of any other unit. However, grep tells me that /usr/lib/systemd/systemd contains the rescue.target string, which worries me. Is there a list of all the units that are required, even though no other unit lists them? ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] minimal required units
Andrei Borzenkov arvidj...@gmail.com wrote on 03/12/2015 12:18:15 PM: From: Andrei Borzenkov arvidj...@gmail.com To: aaron_wri...@selinc.com Cc: systemd-devel@lists.freedesktop.org Date: 03/12/2015 12:18 PM Subject: Re: [systemd-devel] minimal required units В Thu, 12 Mar 2015 11:09:57 -0700 aaron_wri...@selinc.com пишет: I feel like there needs to be a list of required units to get base functionality out of systemd. So that embedded guys like me can build up a system from scratch, instead of starting from full blown desktop support and guessing at what can be taken out. sysinit.target is supposed to get you minimal working system (more or less what you got with single user in the past). It could be considered as starting point. Most embedded systems I have seen were running something very close to single user anyway. Right now, I'm starting with the basic.target. Gets me a few more features than sysinit.target, such as timers, which I feel I can use in my product to replace cron. My question is mainly about whether the list of actual required units is known, or if it is something that requires investigation (digging through a bunch of code). Did you see bootup(7)? Yes, I've read that a few times, and I love the diagram. It seems to suggest to me that I can use basic.target as a good synchronization point, and then add my units after that, which makes sense to me. If I include at least all of the units leading up to basic.target, would that cover the units required by systemd? Though, that would include lots of things I don't need, such as cryptsetup.target, swap.target, mqueue, configfs, debugfs, etc. I'm concerned because I left out local-fs.target to begin with, as I don't need systemd to mount anything, but that seemed to cause systemd to unmount everything other than / and the kernel file systems. So I got bit by there not being any documentation that says, local-fs.target is Required. Unless, I'm missing something. PS - Thanks for pointing me at information. I'm still getting up to speed on systemd. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] minimal required units
man 7 systemd.special On Thu, Mar 12, 2015 at 4:41 PM, aaron_wri...@selinc.com wrote: Andrei Borzenkov arvidj...@gmail.com wrote on 03/11/2015 08:47:43 PM: From: Andrei Borzenkov arvidj...@gmail.com To: aaron_wri...@selinc.com Cc: systemd-devel@lists.freedesktop.org Date: 03/11/2015 08:47 PM Subject: Re: [systemd-devel] minimal required units В Wed, 11 Mar 2015 12:02:29 -0700 aaron_wri...@selinc.com пишет: I'm trying to make an embedded device, and I would like to start with the minimal setup as possible. Are there some units that are required by systemd? I ask because systemd is complaining about a missing rescue.target unit, When does it do it? It was doing this because my default unit was not set correctly. But that isn't really the question. The question is, what units are required by systemd? How can I figure that out? It seems like rescue.target, local-fs.target, and local-fs-pre.target are required, but I've only discovered that after trial and error. I know the systemd.special man page lists a ton of special units, but it seems that not all of them are required. Right? Well, which ones are? I feel like I need to look through the code to see when a hardcoded unit is referenced, like rescue.target was, that I don't know about. My device doesn't have many of the same requirements of a full desktop or server Linux, so I'm trying to strip out things from systemd, unit wise, that I don't want or need. I've customized sysinit.target and basic.target to just reference the units I want. And that seems to be going smooth, but it appears there are other units, that I didn't know about that are required, but that aren't documented as such (that I could find). This scares me a bit. but I don't list rescue.target as a dependency of any other unit. However, grep tells me that /usr/lib/systemd/systemd contains the rescue.target string, which worries me. Is there a list of all the units that are required, even though no other unit lists them? ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] minimal required units
aaron_wri...@selinc.com writes:
Just for illustration purposes, here are few units listed in
systemd.special, that I don't feel like I need, but which I'm left
wondering if systemd needs them:
cryptsetup.target
display-manager.service
getty.target
graphical.target
hibernate.target
hybrid-sleep.target
halt.target
initrd-fs.target
kbrequest.target
multi-user.target
network-online.target
poweroff.target
remote-fs.target
initrd-root-fs.target
runlevel*.target
sigpwr.target
sleep.target
suspend.target
swap.target
The right way to think about targets in systemd is as synchronous
points. If target A Requires target B and is After it, then target A
won't try to start until after target B is ready in the sd_notify()
sense. The targets are part of the signaling system for systemd's
sequencing method. Neil Brown's article at LWN
(https://lwn.net/Articles/584176/) discusses how targets can be used
to pass configuration signals between services.A target that can
be 'isolated' is akin to a run-level, but a target that cannot be
isolated is used for synchronization or signaling.
Some targets may be useful even if you don't strictly need them. For
example, we old people may prefer to append '3' to bootargs when we
want to come up to the text console, and runlevel3.target provides
that capability. You can, assuredly, append
'systemd.unit=multi-user.target' to bootargs instead.
The targets contribute to the file count, but not much to the binary
size.For embedded in general, it seems better not to touch
upstream bits if they don't make the binary larger. Removing
services you don't need also must be done with caution. For example,
I found out the hard way that getting rid of PAM means no 'systemctl
--user' commands will work.
Consider choosing different options when running configure.That
interface should in principle cleanly remove file sets corresponding
to individual features. Removing individual files is always more
dangerous.
-- Alison
--
Alison Chaiken ali...@she-devel.com
650-279-5600
http://{she-devel.com,exerciseforthereader.org}
One consumes a great deal of silence in the course of becoming
educated. -- Matthew B. Crawford
___
systemd-devel mailing list
systemd-devel@lists.freedesktop.org
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Re: [systemd-devel] minimal required units
Andrei Borzenkov arvidj...@gmail.com wrote on 03/12/2015 10:38:19 AM: From: Andrei Borzenkov arvidj...@gmail.com To: aaron_wri...@selinc.com Cc: systemd-devel@lists.freedesktop.org Date: 03/12/2015 10:38 AM Subject: Re: [systemd-devel] minimal required units В Thu, 12 Mar 2015 09:42:25 -0700 aaron_wri...@selinc.com пишет: Peter Sztan sztan...@gmail.com wrote on 03/12/2015 09:33:38 AM: From: Peter Sztan sztan...@gmail.com To: aaron_wri...@selinc.com Cc: systemd Mailing List systemd-devel@lists.freedesktop.org Date: 03/12/2015 09:33 AM Subject: Re: [systemd-devel] minimal required units Sorry for the noise, I have now read that you have already seen it. Just for illustration purposes, here are few units listed in systemd.special, that I don't feel like I need, but which I'm left wondering if systemd needs them: cryptsetup.target display-manager.service getty.target graphical.target hibernate.target hybrid-sleep.target halt.target initrd-fs.target kbrequest.target multi-user.target network-online.target poweroff.target remote-fs.target initrd-root-fs.target runlevel*.target sigpwr.target sleep.target suspend.target swap.target targets serve as common reference for collection of other units (services). They do not do anything by themselves, there is absolutely no reason to remove them. Some of them (at least those mentioned in systemd.special) do have special meaning and removing them will actually break functionality. In my embedded environment I have to justify everything on the product. Given that the product doesn't have a monitor, I find that targets such as graphical.target or display-manager.target for example are hard to justify. I would rather not just throw the whole systemd-kitchen-sink at the product and call it a day. It seems obvious that not all of the units referenced in systemd.special are actually required. Some of them don't even exist with my configuration (dbus.service, dbus.socket, runlevel*.target, etc). I feel like there needs to be a list of required units to get base functionality out of systemd. So that embedded guys like me can build up a system from scratch, instead of starting from full blown desktop support and guessing at what can be taken out. My question is mainly about whether the list of actual required units is known, or if it is something that requires investigation (digging through a bunch of code). ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] minimal required units
В Thu, 12 Mar 2015 11:09:57 -0700 aaron_wri...@selinc.com пишет: I feel like there needs to be a list of required units to get base functionality out of systemd. So that embedded guys like me can build up a system from scratch, instead of starting from full blown desktop support and guessing at what can be taken out. sysinit.target is supposed to get you minimal working system (more or less what you got with single user in the past). It could be considered as starting point. Most embedded systems I have seen were running something very close to single user anyway. My question is mainly about whether the list of actual required units is known, or if it is something that requires investigation (digging through a bunch of code). Did you see bootup(7)? ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] minimal required units
В Wed, 11 Mar 2015 12:02:29 -0700 aaron_wri...@selinc.com пишет: I'm trying to make an embedded device, and I would like to start with the minimal setup as possible. Are there some units that are required by systemd? I ask because systemd is complaining about a missing rescue.target unit, When does it do it? but I don't list rescue.target as a dependency of any other unit. However, grep tells me that /usr/lib/systemd/systemd contains the rescue.target string, which worries me. Is there a list of all the units that are required, even though no other unit lists them? ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
