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Old 03-16-2012, 08:40 PM
Canek Peláez Valdés
 
Default To mount or not to Mount proc, that is the question

On Fri, Mar 16, 2012 at 3:18 PM, Mark Knecht <markknecht@gmail.com> wrote:
> On Fri, Mar 16, 2012 at 12:47 PM, Canek Peláez Valdés <caneko@gmail.com> wrote:
>> On Fri, Mar 16, 2012 at 1:40 PM, Mark Knecht <markknecht@gmail.com> wrote:
> <SNIP>
>>> Looking at the Gentoo amd64 install guide here:
>>>
>>> http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?part=1&chap=8
>>>
>>> it appears that the recommendation is to mount proc.
>>>
>>> [quote]
>>>
>>> /dev/sda1 * /boot * * * *ext2 * *defaults,noatime * * 1 2
>>> /dev/sda2 * none * * * * swap * *sw * * * * * * * * * 0 0
>>> /dev/sda3 * / * * * * * *ext3 * *noatime * * * * * * *0 1
>>>
>>> /dev/cdrom */mnt/cdrom * auto * *noauto,user * * * * *0 0
>>>
>>> proc * * * */proc * * * *proc * *defaults * * * * * * 0 0
>>> shm * * * * /dev/shm * * tmpfs * nodev,nosuid,noexec *0 0
>>>
>>> [quote]
> <SNIP>
>>
>> I haven't put /proc explicitly on my /etc/fstab since a long time ago,
>> and everything seems to be working. However, I use systemd, which
>> always mounts /proc with the default options, and only uses the entry
>> in /etc/fstab (if present) to override the default options. In other
>> words, systemd always mounts /proc, no matter if it's listed in
>> /etc/fstab or not.
>>
>> I don't know what OpenRC does, but it would not surprise me that it's
>> something similar.
>>
>> Regards.
>> --
>> Canek Peláez Valdés
>> Posgrado en Ciencia e Ingeniería de la Computación
>> Universidad Nacional Autónoma de México
>>
>
> Thanks Canek. I appreciate your response.
>
> It seems when rereading the link above the authors do put the work
> 'example' in italics, implying that possibly I should know what I'm
> doing and not depend on the text on that page. I'm fine with the not
> depending part. I'm not so sure about the 'know what I'm doing' part.
> ;-)
>
> I'm going to take a wild guess that it's somehow mounted in an init
> script these days but I have no reason to know that's actually how it
> gets done. I did read the kernel docs and it doesn't seem to be done
> automatically by the kernel AFAICT.

No, it's the init system; look at /lib/rc/sh/init.sh:66:

# By default VServer already has /proc mounted, but OpenVZ does not!
# However, some of our users have an old proc image in /proc
# NFC how they managed that, but the end result means we have to test if
# /proc actually works or not. We do this by comparing two reads of
# /proc/self/environ for which we have set the variable VAR to two
# different values. If the comparison comes back equal, we know that
# /proc is not working.
mountproc=true
f=/proc/self/environ
if [ -e $f ]; then
if [ "$(VAR=a cat $f)" = "$(VAR=b cat $f)" ]; then
eerror "You have cruft in /proc that should be deleted"
else
einfo "/proc is already mounted, skipping"
mountproc=false
fi
fi
unset f

if $mountproc; then
procfs="proc"
[ "$RC_UNAME" = "GNU/kFreeBSD" ] && proc="linprocfs"
ebegin "Mounting /proc"
if ! fstabinfo --mount /proc; then
mount -n -t "$procfs" -o noexec,nosuid,nodev proc /proc
fi
eend $?
fi

Mistery solved

Regards.
--
Canek Peláez Valdés
Posgrado en Ciencia e Ingeniería de la Computación
Universidad Nacional Autónoma de México
 
Old 03-16-2012, 08:50 PM
Mark Knecht
 
Default To mount or not to Mount proc, that is the question

On Fri, Mar 16, 2012 at 2:40 PM, Canek Peláez Valdés <caneko@gmail.com> wrote:
> On Fri, Mar 16, 2012 at 3:18 PM, Mark Knecht <markknecht@gmail.com> wrote:
>> On Fri, Mar 16, 2012 at 12:47 PM, Canek Peláez Valdés <caneko@gmail.com> wrote:
>>> On Fri, Mar 16, 2012 at 1:40 PM, Mark Knecht <markknecht@gmail.com> wrote:
>> <SNIP>
>>>> Looking at the Gentoo amd64 install guide here:
>>>>
>>>> http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?part=1&chap=8
>>>>
>>>> it appears that the recommendation is to mount proc.
>>>>
>>>> [quote]
>>>>
>>>> /dev/sda1 * /boot * * * *ext2 * *defaults,noatime * * 1 2
>>>> /dev/sda2 * none * * * * swap * *sw * * * * * * * * * 0 0
>>>> /dev/sda3 * / * * * * * *ext3 * *noatime * * * * * * *0 1
>>>>
>>>> /dev/cdrom */mnt/cdrom * auto * *noauto,user * * * * *0 0
>>>>
>>>> proc * * * */proc * * * *proc * *defaults * * * * * * 0 0
>>>> shm * * * * /dev/shm * * tmpfs * nodev,nosuid,noexec *0 0
>>>>
>>>> [quote]
>> <SNIP>
>>>
>>> I haven't put /proc explicitly on my /etc/fstab since a long time ago,
>>> and everything seems to be working. However, I use systemd, which
>>> always mounts /proc with the default options, and only uses the entry
>>> in /etc/fstab (if present) to override the default options. In other
>>> words, systemd always mounts /proc, no matter if it's listed in
>>> /etc/fstab or not.
>>>
>>> I don't know what OpenRC does, but it would not surprise me that it's
>>> something similar.
>>>
>>> Regards.
>>> --
>>> Canek Peláez Valdés
>>> Posgrado en Ciencia e Ingeniería de la Computación
>>> Universidad Nacional Autónoma de México
>>>
>>
>> Thanks Canek. I appreciate your response.
>>
>> It seems when rereading the link above the authors do put the work
>> 'example' in italics, implying that possibly I should know what I'm
>> doing and not depend on the text on that page. I'm fine with the not
>> depending part. I'm not so sure about the 'know what I'm doing' part.
>> ;-)
>>
>> I'm going to take a wild guess that it's somehow mounted in an init
>> script these days but I have no reason to know that's actually how it
>> gets done. I did read the kernel docs and it doesn't seem to be done
>> automatically by the kernel AFAICT.
>
> No, it's the init system; look at /lib/rc/sh/init.sh:66:
>
> # By default VServer already has /proc mounted, but OpenVZ does not!
> # However, some of our users have an old proc image in /proc
> # NFC how they managed that, but the end result means we have to test if
> # /proc actually works or not. We do this by comparing two reads of
> # /proc/self/environ for which we have set the variable VAR to two
> # different values. If the comparison comes back equal, we know that
> # /proc is not working.
> mountproc=true
> f=/proc/self/environ
> if [ -e $f ]; then
> * * * *if [ "$(VAR=a cat $f)" = "$(VAR=b cat $f)" ]; then
> * * * * * * * *eerror "You have cruft in /proc that should be deleted"
> * * * *else
> * * * * * * * *einfo "/proc is already mounted, skipping"
> * * * * * * * *mountproc=false
> * * * *fi
> fi
> unset f
>
> if $mountproc; then
> * * * *procfs="proc"
> * * * *[ "$RC_UNAME" = "GNU/kFreeBSD" ] && proc="linprocfs"
> * * * *ebegin "Mounting /proc"
> * * * *if ! fstabinfo --mount /proc; then
> * * * * * * * *mount -n -t "$procfs" -o noexec,nosuid,nodev proc /proc
> * * * *fi
> * * * *eend $?
> fi
>
> Mistery solved
>
> Regards.
> --
> Canek Peláez Valdés
> Posgrado en Ciencia e Ingeniería de la Computación
> Universidad Nacional Autónoma de México
>

Yep, that's it. Somewhat interestingly it was at line 89 in my file
but that may well be differences between OpenRC and systemd, etc.
Anyway, the code looks identical and at least on the one machine I've
tested it doesn't seem to have hurt anythign to remove it from my
fstab file.

!Thanks!

Cheers,
Mark
 

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