Re: [gentoo-user] What to put in chroot mtab

[J. Roeleveld]

On 1 August 2014 23:33:05 CEST, "Canek Peláez Valdés" <caneko@×××××.com> wrote:
>On Fri, Aug 1, 2014 at 4:31 PM, Canek Peláez Valdés <caneko@×××××.com>
>wrote:
>> On Aug 1, 2014 3:46 PM, "J. Roeleveld" <joost@××××××××.org> wrote:
>>>
>>> On 1 August 2014 15:28:01 CEST, Dale <rdalek1967@×××××.com> wrote:
>>> >Peter Humphrey wrote:
>>> >> On Friday 01 August 2014 14:07:08 I wrote:
>>> >>
>>> >>> I run a couple of chroots on this box to build packages for
>other
>>> >boxes on
>>> >>> the LAN. So far, I haven't worked out what I should populate
>>> >/etc/mtab with
>>> >>> in each chroot. Is it enough to "grep ext4 /etc/mtab >
>>> >>> /mnt/chroot/etc/mtab"? That catches all the physical partitions,
>but
>>> >I
>>> >>> imagine I need to add some /proc, /sys and /dev entries as well,
>but
>>> >is
>>> >>> there a simple formula for doing this?
>>> >> I meant to add that one chroot is 32-bit and the other is 64. The
>>> >host is an
>>> >> i5 running openrc.
>>> >>
>>> >
>>> >It has been a good while since I used this.  So, make sure it makes
>>> >sense to you before trying this.  This may not work if something
>has
>>> >changed in the past several years.  Use with caution if at all.
>>> >
>>> >This is a little script, if you want to call it that, that I used
>to do
>>> >mine.  It also lists the command to use to do a 32 bit chroot from
>a 64
>>> >bit rig.  Here it is:
>>> >
>>> >root@fireball / # cat /root/xx.chroot-mount-32bit
>>> >
>>> >
>>> >mount -o bind /dev /mnt/gentoo32/dev
>>> >mount -o bind /dev/pts /mnt/gentoo32/dev/pts
>>> >mount -o bind /dev/shm /mnt/gentoo32/dev/shm
>>> >mount -o bind /proc /mnt/gentoo32/proc
>>> >mount -o bind /proc/bus/usb /mnt/gentoo32/proc/bus/usb
>>> >mount -o bind /sys /mnt/gentoo32/sys
>>> >mkdir -p /mnt/gentoo32/usr/portage/
>>> >mount -o bind /usr/portage /mnt/gentoo32/usr/portage/
>>> >
>>> >
>>> >echo " mounting finished"
>>> >
>>> >echo "run linux32 chroot /mnt/gentoo32 /bin/bash next"
>>> >root@fireball / #
>>> >
>>> >
>>> >You may have different mount points at the very least so edit to
>match
>>> >what you have.  Again, things could have changed and that no longer
>>> >will
>>> >work.  It may not be a bad idea to let someone who has done this
>more
>>> >recently to give a thumbs up to that.
>>> >
>>> >That last command should be:
>>> >
>>> >linux32 chroot /mnt/gentoo32 /bin/bash
>>> >
>>> >Dale
>>> >
>>> >:-)  :-)
>>>
>>> That script is too long :)
>>>
>>> cd /mnt/gentoo
>>> mount -o rbind /dev dev
>>> mount -o rbind /sys sys
>>> mount -o rbind /proc proc
>>> cp -L /etc/resolv.conf etc/resolv.conf
>>> cd ..
>>> chroot gentoo /bin/bash
>>>
>>> To undo:
>>> cd /mnt/gentoo
>>> umount -l proc sys dev
>>
>> That's still too long :)
>>
>> With systemd-nspawn, you only do:
>>
>> systemd-nspawn -D /mnt/gentoo
>>
>> Systemd takes care of /dev, /sys, etc. If the container has systemd
>> installed, you can do
>>
>> systemd-nspawn -bD /mnt/gentoo
>>
>> and the services inside the container will be started like in a
>regular boot
>> (you'll need to set the root password for the container).
>>
>> Also, if you want to share the /usr/portage directory between host
>and
>> container, you only need to
>>
>> systemd-nspawn --bind=/usr/portage -bD /mnt/gentoo
>
>Oh, and I forgot: to stop the container, just log out if the container
>runs OpenRC, or run systemctl poweroff if the container runs systemd.
>
>Regards.

That script could easily be written in C and compiled and then called in a similar way as systemd-nspawn.

What your command does is basically the same apart from doing something different from using chroots.

Converting a perfectly working and efficiently running system to use something like systemd just to have a chroot environment is overly complex and convoluted. 
These solutions often cause more issues then the problem it tried to solve.

--
Joost
-- 
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