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dcljr
Tux's lil' helper
Joined: 20 Aug 2005
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Location: Austin, TX
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 Posted: Tue Jun 07, 2011 4:29 pm Post subject: different forms of mount commands for proc and dev |
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At the point in the standard installation process (i.e., from a minimal installation CD) where proc and /dev are mounted in preparation for chrooting, the Handbook says (in Pt. 1, Ch. 6, "Code Listing 1.4"):
| Quote: | # mount -t proc none /mnt/gentoo/proc
# mount --rbind /dev /mnt/gentoo/dev |
OTOH, The Gentoo Linux alternative installation method HOWTO, under "Installation from non-Gentoo LiveCDs", says:
| Quote: | when you are asked to mount the proc system, issue the following command instead:
[...]
# mount -o bind /proc /mnt/gentoo/proc |
But the same HOWTO, under "Installing Gentoo from an existing Linux distribution", doesn't say anything special about mounting proc and /dev (i.e., just follow the Handbook).
And the Gentoo Linux x86 Quick Install Guide (which assumes booting from a minimal installation CD) says:
| Quote: | livecd / # mount -t proc proc /mnt/gentoo/proc
livecd / # mount --rbind /dev /mnt/gentoo/dev |
Finally, in some "tips" I wrote up for myself a couple of years ago about how to install Gentoo from an existing (running) Gentoo system, which I presumably based on what the Handbook and the Alternative HOWTO said at the time:
| Quote: | # mount -o bind /proc /mnt/gentoo/proc
# mount -o bind /dev /mnt/gentoo/dev |
But then later in the same document, when describing how to stop the installation process and resume it later, I have written:
| Quote: | # mount -t proc none /mnt/gentoo/proc
# mount -o bind /dev /mnt/gentoo/dev |
Hmm. So, I guess one of those is a mistake, since I see no good reason for the mounting of proc to be different the second (third, etc.) time versus the first time.
So here's my question: What's the difference between all these mount commands?
I (think I) understand that -o bind is used for already mounted filesystems (note the "/" in front of proc in the -o bind versions), and that --rbind is essentially just a more robust version of -o bind that includes any "submounts" within the specified "subtree".
But why is -t proc used when you've booted from a CD? And is there any difference between -t proc none and -t proc proc?
Last edited by dcljr on Thu Dec 22, 2011 3:03 pm; edited 1 time in total |
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NeddySeagoon
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| Posted: Tue Jun 07, 2011 6:42 pm Post subject: |
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dcljr,
Allow me to refer you to
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Ant P.
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Joined: 18 Apr 2009
Posts: 6920
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| Posted: Tue Jun 07, 2011 8:37 pm Post subject: Re: different forms of mount commands for proc and dev |
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| dcljr wrote: | | is there any difference between -t proc none and -t proc proc? |
procfs isn't a real filesystem, so the second word is just used as a label instead of giving a device name to mount from. |
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NeddySeagoon
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| Posted: Wed Jun 08, 2011 10:03 pm Post subject: |
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dcljr,
-t proc none
Gives you an error message "none busy" in certain umount conditions
-t proc proc?
Gives "proc busy" in the same conditions.
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NeddySeagoon
Computer users fall into two groups:-
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dcljr
Tux's lil' helper
Joined: 20 Aug 2005
Posts: 139
Location: Austin, TX
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| Posted: Thu Dec 22, 2011 3:00 am Post subject: |
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I'm "resurrecting" this thread because I need more information. The answers above only seem to address the most minor of my questions, the difference between "none" and "proc" in the proc-mounting command (and, BTW, let's pretend like I've actually read the man page for mount but still need someone to explain this to me).
The important question is this: why is it that when you've booted from the installation CD or when you're installing from an existing Linux distribution, you can use the "regular" (i.e., from the Handbook) version:
| Quote: | | # mount -t proc none /mnt/gentoo/proc |
but when you're installing from a "non-Gentoo LiveCD", you're supposed to use:
| Quote: | | # mount -o bind /proc /mnt/gentoo/proc |
What is the fundamental difference between the scenarios that necessitate the different forms of the command? |
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Hu
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| Posted: Thu Dec 22, 2011 3:05 am Post subject: |
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| If /proc is already a procfs, then you can bind mount it into other places where you need a procfs. If it is not, or if you are not sure, then you need to mount a procfs at the desired location. |
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dcljr
Tux's lil' helper
Joined: 20 Aug 2005
Posts: 139
Location: Austin, TX
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| Posted: Thu Dec 22, 2011 9:24 am Post subject: |
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| Hu wrote: | | If /proc is already a procfs, then you can bind mount it into other places where you need a procfs. If it is not, or if you are not sure, then you need to mount a procfs at the desired location. |
Hmm. So am I to understand that when someone boots from a "non-Gentoo LiveCD", they are guaranteed to have a procfs mounted at /proc, but if they boot from the installation CD or anything else ("an existing Linux distribution") they aren't? That doesn't make sense to me. How can you have a running Linux system without a procfs mounted at /proc?
Also, the fact that you say "or if you are not sure" makes it sound like it's optional, or something — as if you could just always use the second ("-t proc") form. But that can't be true, otherwise they wouldn't have to tell people specifically to use the "-o bind" version in the "alternative installation" HOWTO. So why do they tell people that? |
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John R. Graham
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| Posted: Thu Dec 22, 2011 12:33 pm Post subject: |
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You're overthinking this. In all cases (I believe), the Handbook form is acceptable. You're also talking about a nuance that can have no effect whatsoever on your eventual installed Gentoo system.
- John
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dcljr
Tux's lil' helper
Joined: 20 Aug 2005
Posts: 139
Location: Austin, TX
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| Posted: Thu Dec 22, 2011 3:14 pm Post subject: |
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| John R. Graham wrote: | | In all cases (I believe), the Handbook form is acceptable. You're also talking about a nuance that can have no effect whatsoever on your eventual installed Gentoo system. |
That answered my question! Thank you! 
Bu-u-u-t...
The HOWTO sez (slightly edited to remove code snippet "titles"):
| Quote: | [...] Next, you'll need to create the /mnt/gentoo mountpoint.
| Code: | | # mkdir /mnt/gentoo |
At this point, you can pick up with the standard install documentation at part 4. However, when you are asked to mount the proc system, issue the following command instead:
| Code: | | # mount -o bind /proc /mnt/gentoo/proc |
When you're ready to unpack the stage tarball in part 5 [...] |
That certainly makes it look like it's important to use a different form of the command! Are you telling me one of the authors went to the trouble of including this instruction for absolutely no reason? |
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John R. Graham
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| Posted: Thu Dec 22, 2011 3:16 pm Post subject: |
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Well, I'm sure the author had a reason, if only for personal preference. However, this is like having an intricate and abstruse discussion about the color of paint on the scaffolding that the brickmasons use to lay the brick for your house. The question is, "How does this affect your house?"
- John
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Installing Gentoo
