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#1 2005-02-21 09:06:52

pixel
Member
From: Living in the Server Room
Registered: 2005-02-21
Posts: 119

How to get rid of BOTH udev and devfs?

Let me say first that I love Arch. I was using Slackware before and feel at home here but one thing that REALLY annoys me is that Arch developers force people during installation to install devfs with all those silly device names like /dev/discs/disc0/partX, what kind of bull... is that? I like traditional device names, at least we should have the option to install it or NOT. Personally i don't need hotplug, devfs or udev, I'm not really changing anything in my hardware, so why bother?

Now my question is - how to get rid of BOTH devfs and udev, I want to erase it COMPLETELY from my system. I already compiled a new kernel WITHOUT support for devfs, but i see that /dev directory is all messed up with all those devfs symlinks, what i can safely delete?

also, if i delete both udev and devfs and later for example after compiling a new kernel the system wont boot so that i will be forced to use Arch install cd to boot, will it be working? I mean Arch install cd uses devfs names and when i delete all the symlinks in my /dev will it be able to boot into my system?

Thank you for all the answers.


Favorite systems: ArchLinux, OpenBSD
"Yes, I love UNIX"

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#2 2005-02-21 12:35:11

jp_fielding
Member
Registered: 2004-08-28
Posts: 85

Re: How to get rid of BOTH udev and devfs?

actually, while the kernel has it compiled in, i pick udev from base, unselect devfs, apply the devfs=nomount line to my kernel, and change the devices names from fstab back to traditional names all before i'm done with the install.  post install i recompile a stripped kernel without devfs support and that's the end of devfs.

as for getting rid of udev too, that's a question for someone else. it would seem as simply as simply not installing hotplug or udev, but that's because i'm past knowing what i'm talking about.

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#3 2005-02-21 12:50:34

rasat
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From: Finland, working in Romania
Registered: 2002-12-27
Posts: 2,176
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Re: How to get rid of BOTH udev and devfs?

Without Devfs or UDev the directory /dev remains empty.... either one has to run for Arch to work. Other distros use static device system with ready made devices and symlinks.

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#4 2005-02-21 14:12:15

Moo-Crumpus
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From: Hessen / Germany
Registered: 2003-12-01
Posts: 1,444

Re: How to get rid of BOTH udev and devfs?


Frumpus addict
[mu'.krum.pus], [frum.pus]

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#5 2005-02-21 14:12:43

pixel
Member
From: Living in the Server Room
Registered: 2005-02-21
Posts: 119

Re: How to get rid of BOTH udev and devfs?

jp_fielding, I know about that method, but still your /dev is all messed up with those /dev/discs/disc0/partX stuff
Why use udev on a server and waste memory running that process at all?

rasat, exactly, I found at the wiki here http://wiki2.archlinux.org/index.php/Sw … om%20devfs
that to get it to work i need to recreate the whole /dev structure manually or with script that is available online.. gosh I'm not in the mood really to play with all that, i just need to quick deploy some servers and have them configured the way i want it (read /dev/hda instead of /dev/discs/disc0/partX), well i fear i will use Slack 10.1 instead of Arch for that task, at least everything is working there out-of-the-box.

I think Arch would be a perfect distro (very Slack-like plus superb pacman) IF ONLY udev or devfs would not be installing itself on default.
Why the main developers behind the boards do not let people decide for themselves, I think many of them would like to have static /dev
As i see it right now it's impossible without MUCH messing around the system and praying...


Favorite systems: ArchLinux, OpenBSD
"Yes, I love UNIX"

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#6 2005-02-21 15:10:37

rasat
Forum Fellow
From: Finland, working in Romania
Registered: 2002-12-27
Posts: 2,176
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Re: How to get rid of BOTH udev and devfs?

pixel wrote:

....i want it (read /dev/hda instead of /dev/discs/disc0/partX)

In DevFs and UDev you don't need to use /dev/discs/disc0/partX. In my /etc/fstab I use static device syntax.

/dev/hda5 swap swap defaults 0 0
/dev/hda2 / ext3 defaults 0 0
/dev/hda3 /home ext3 defaults 0 0
/dev/hda6 /work ext3 defaults 0 0
/dev/hda7 /save ext3 defaults 0 0
/dev/hda1 /mnt/win_c vfat user,uid=rasat,gid=users 0 0
# /dev/sda1  /mnt/usb  auto  defaults 0 0

DevFs is messy but UDev is clean, organized and appears same as the static device system.

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#7 2005-02-21 15:30:30

pixel
Member
From: Living in the Server Room
Registered: 2005-02-21
Posts: 119

Re: How to get rid of BOTH udev and devfs?

ok, I get you, but like i said you still got your /dev not static and need to
have udev process on all the time. IMHO for production servers static /dev is more stable. Udev is still in development after all, it's rather a *new* thing for linux.


Favorite systems: ArchLinux, OpenBSD
"Yes, I love UNIX"

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#8 2005-02-21 15:44:05

phrakture
Arch Overlord
From: behind you
Registered: 2003-10-29
Posts: 7,879
Website

Re: How to get rid of BOTH udev and devfs?

pixel wrote:

ok, I get you, but like i said you still got your /dev not static and need to
have udev process on all the time. IMHO for production servers static /dev is more stable. Udev is still in development after all, it's rather a *new* thing for linux.

do some profiling on udev - it's idle, and even swapped out a vast majority of the time.... if the server is any good, it'll consume the resources of another bash session

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#9 2005-02-21 15:59:40

rasat
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From: Finland, working in Romania
Registered: 2002-12-27
Posts: 2,176
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Re: How to get rid of BOTH udev and devfs?

From my two years of experience on this forum, users first using DevFs and later UDev, very few complained about these device systems (I was one of them who complained when joining. smile ... until today using static syntax).

A static system doesn't mean a hardware will work.... the right module and configure has to be there. But in DevFS or UDev if the device appears in /dev then hardware will most likely also run. I have experienced more headage with the static than dynamic system. But that's me and everyone has their own experience.

You are using for a server, in this regard I have no experience.

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#10 2005-02-21 16:54:10

pixel
Member
From: Living in the Server Room
Registered: 2005-02-21
Posts: 119

Re: How to get rid of BOTH udev and devfs?

you know what? y'all convinced me to give it a try... I see also that new Slackware comes with udev too now, so if even Patrick included it in his base system
http://www.slackware.com/pb/searchpkg.p … tring=udev he must have regarded it as pretty stable  lol
After all i know that udev is the future and considering this i feel Arch is also the future, it's much easier to update and keep track of all the packages with dependencies than Slack (even with slapt-get/swaret). One thing i don't like in Slackware is a lack of centralized repository with ALL available packages  (linuxpackages.net is good but it still feels like a third-party solution). Arch has excellent central repository and really lovely package manager..I guess that's what really counts in choosing the right distribution.

Thanks for all the suggestions.


Favorite systems: ArchLinux, OpenBSD
"Yes, I love UNIX"

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#11 2005-02-21 16:59:04

sarah31
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From: Middle of Canada
Registered: 2002-08-20
Posts: 2,975
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Re: How to get rid of BOTH udev and devfs?

pfft. if you don't like the /dev structure and don't want to change it then by all means use something else.  A static /dev tree is an ancient inefficient method where you are stuck with as many useless /dev entries. You also9 have to do all sorts of other silly symlinks etc.

BTW you should know that your "traditional" dev tree is something pretty much exclusive to Linux. If you look at the BSD or old UNIX means of naming devices such as partitions is very much different and even more "complex" than devfs or udev.

Anyway so very few people have ever bitched about not having a static dev tree that it is pretty much a moot point and condemning the devs and distro for it is retarded.


AKA uknowme

I am not your friend

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#12 2005-02-21 17:09:01

pixel
Member
From: Living in the Server Room
Registered: 2005-02-21
Posts: 119

Re: How to get rid of BOTH udev and devfs?

sarah, dont be so negative minded, it's bad for your health  big_smile
I only stated it would be nice to have a choice during install whether we want static /dev or not. I think also that Arch should have udev as DEFAULT and definetly not devfs which is a total mess.


Favorite systems: ArchLinux, OpenBSD
"Yes, I love UNIX"

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#13 2005-02-21 17:17:27

pixel
Member
From: Living in the Server Room
Registered: 2005-02-21
Posts: 119

Re: How to get rid of BOTH udev and devfs?

also another question, do i REALLY need to have hotplug installed if i want to use udev? I will not be using any USB etc hardware with this machine...


Favorite systems: ArchLinux, OpenBSD
"Yes, I love UNIX"

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#14 2005-02-21 19:11:10

iBertus
Member
From: Greenville, NC
Registered: 2004-11-04
Posts: 2,228

Re: How to get rid of BOTH udev and devfs?

pixel wrote:

also another question, do i REALLY need to have hotplug installed if i want to use udev? I will not be using any USB etc hardware with this machine...

I don't run hotplug and everything works fine here. Just add the modules you need to rc.conf and you should be good.

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#15 2005-02-21 19:43:03

phrakture
Arch Overlord
From: behind you
Registered: 2003-10-29
Posts: 7,879
Website

Re: How to get rid of BOTH udev and devfs?

pixel wrote:

also another question, do i REALLY need to have hotplug installed if i want to use udev? I will not be using any USB etc hardware with this machine...

hotplug has two parts - the hotplug "subsystem" and the daemon... you need hotplug, as udev calls the hotplug scripts to properly setup a new device... the daemon, however, you don't need

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#16 2005-02-21 21:27:34

skoal
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From: Frequent Flyer Underworld
Registered: 2004-03-23
Posts: 612
Website

Re: How to get rid of BOTH udev and devfs?

One other reason why you should can a static /dev mount is filesystem corruption.  If "fsck" targets those entry points, that will convince you quick to use devfs or udev.

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#17 2005-02-21 22:45:01

pixel
Member
From: Living in the Server Room
Registered: 2005-02-21
Posts: 119

Re: How to get rid of BOTH udev and devfs?

phrakture wrote:

hotplug has two parts - the hotplug "subsystem" and the daemon... you need hotplug, as udev calls the hotplug scripts to properly setup a new device... the daemon, however, you don't need

Could you elaborate more on that? As i understand it now i need to install hotplug package (it is already in the base), but post install i can disable hotplug deamon right? (I'm using udev now)


Favorite systems: ArchLinux, OpenBSD
"Yes, I love UNIX"

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#18 2005-02-22 10:03:23

iphitus
Forum Fellow
From: Melbourne, Australia
Registered: 2004-10-09
Posts: 4,927

Re: How to get rid of BOTH udev and devfs?

Hotplug does not need to be running. i havnt ever run it and dont really have any intention or need to.

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#19 2005-02-22 12:23:54

lanrat
Member
From: Poland
Registered: 2003-10-28
Posts: 1,274

Re: How to get rid of BOTH udev and devfs?

There are so many questions about hotplug/udev/devfs that I think a few things need to be explained:

http://linux-hotplug.sourceforge.net

Hotplug lets you plug in new devices and use them immediately. That means that users won't need to learn so much system administration; systems will at least partially autoconfigure themselves. Initially, hotplug included support for USB and PCI (Cardbus) devices, and could automatically configure some common network interfaces. Updated versions include IEEE 1394 (Firewire/i.Link) support and can download firmware to USB devices that need it. On mainframes, S/390 channel devices uses hotplugging to report device attach and other state change events. For laptops, newer kernels also include support for reporting docking station activity.

In the Linux 2.6 kernel, hotplugging has been integrated with the driver model core so that any bus or class can report hotplug events when devices are added or removed.

The Linux kernel will call out to a program, normally /sbin/hotplug, when devices are hotplugged.

ColdPlugging
Hotplugging happens after the kernel OS is running, but there's a closely related problem: what happens before the OS is fully bootstrapped (with all system services available)? By analogy, that problem is called "coldplugging". The simple way to handle this is to make devices connected before hotplugging look like they came along a bit later.

That's basically what "hotplug daemon" in /etc/rc.conf does. You can start it manually with /etc/rc.conf start and see which modules are loaded automatically (compare the output of lsmod before and after). Coldplug is not ideal because it tries to load all modules for the devices that are found by it. For example I have a pararell port (lpt) but I don't use it (I have usb printer). Coldplug finds the port and loads parport module. You can load only the modules that you need from /etc/rc.conf and disable hotplug daemon in /etc/rc.conf.

More info is available in the forums/wiki and on the hotplug/udev sites.

EDIT: I've found my old post. Here are some useful links that will help you better understand the whole thing:
http://portal.suse.com/sdb/en/2004/05/9 … tplug.html
http://wiki.linuxquestions.org/wiki/Hotplug
http://wiki.linuxquestions.org/wiki/Udev

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#20 2005-02-22 13:33:08

pixel
Member
From: Living in the Server Room
Registered: 2005-02-21
Posts: 119

Re: How to get rid of BOTH udev and devfs?

thanks lanrat


Favorite systems: ArchLinux, OpenBSD
"Yes, I love UNIX"

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