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Odysseus
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PostPosted: Wed Jan 23, 2013 10:44 pm    Post subject: a devtmpfs fstab question Reply with quote

I'm a longtime Gentoo user(over 10 years), but I'm a truck driver not a programmer. I'm running ~amd64 on my laptop and also using baselayout-2.

This afternoon while updating my system I saw there an alert that there was a new news item to read.

The alert was titled "2013-01-23-udev-upgrade" and reads as follows:
Quote:
Title Upgrading udev from 171 (or older) to 197
Author Samuli Suominen <ssuominen@gentoo.org>
Posted 2013-01-23
Revision 1

Upgrading udev from 171 (or older) to 197 will require special attention:

- Remove udev-postmount from runlevels.

- The need of CONFIG_DEVTMPFS=y in the kernel; need to verify the fstype for
possible /dev line in /etc/fstab is devtmpfs (and not, for example, tmpfs)

- The case of predictable network interface names; if the file
/etc/udev/rules.d/70-persistent-net.rules is being used for renaming
network interface names to already existing names, then you need to
read following bug[1] because it's no longer possible. This won't
be a problem with the new predictable network interface name scheme[2].

[1] http://bugs.gentoo.org/453494
[2] http://www.freedesktop.org/wiki/Software/systemd/
PredictableNetworkInterfaceNames

- Support for older kernels than 2.6.39 is dropped. If you need older kernel
we recommend you to look into sys-fs/eudev or use local overlay for keeping
the old ebuild. Remember to also get the distfiles where the patchsets are.
The upgrade into current stable version of gentoo-sources is recommended.

- The case of separate /usr; if it worked for you with 171 it will continue
to work for you with 197. We still recommend initramfs with separate /usr
mounting capabilities because you might need packages like sys-apps/kbd
(keymaps in /usr) or net-wireless/bluez (possible keyboard) in early boot.

And read every message printed by the emerge of udev and udev-init-scripts
to ensure the system is in order before booting as this news item might
not be complete.

Apologies if this news came too late for you.


My questions are as follows:

I don't use an initramfs and have never used one. I moved '/usr' and '/var' to '/' about a year ago when I read about an upcoming udev update that would break systems with no initramfs having '/usr' and '/var' mounted on separate partitions. Is this news alert telling me that for some reason I need to make an initramfs now?

I have devtmps properly compiled into my kernel and have done so for quite some time, but I don't have any references to devtmpfs, tmpfs, shm or any other 'temp' file systems in my fstab. I removed them a while back when I noticed they were being created automagically by during startup by various boot scripts in '/etc/init.d'.

My fstab looks like this:
Code:
# <fs>          <mountpoint>   <type>   <opts>         <dump/pass>
/dev/sda7   /      ext4   defaults,relatime   1 1
/dev/sda8   /home      ext4   defaults,relatime   1 2
/dev/sda9   /usr/portage   ext4   defaults,relatime   1 2
/dev/sda5   /boot      ext2   noauto,relatime      1 2
/dev/sda6   none      swap   sw         0 0
#tmpfs      /dev/shm   tmpfs   defaults      0 0
#proc      /proc      proc   defaults      0 0
#sysfs      /sys      sysfs   defaults      0 0
#devpts      /dev/pts   devpts   defaults      0 0


As you can see I've commented out all references to any temp file systems from my fstab.

My mtab looks like this:
Code:
rootfs / rootfs rw 0 0
/dev/root / ext4 rw,relatime,commit=0 0 0
devtmpfs /dev devtmpfs rw,relatime,size=1668232k,nr_inodes=417058,mode=755 0 0
proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
tmpfs /run tmpfs rw,nosuid,nodev,relatime,mode=755 0 0
devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620 0 0
shm /dev/shm tmpfs rw,nosuid,nodev,noexec,relatime 0 0
sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
securityfs /sys/kernel/security securityfs rw,nosuid,nodev,noexec,relatime 0 0
/dev/sda8 /home ext4 rw,relatime,commit=0 1 2
/dev/sda9 /usr/portage ext4 rw,relatime,commit=0 1 2
/dev/sda5 /boot ext2 noauto,relatime 1 2
binfmt_misc /proc/sys/fs/binfmt_misc binfmt_misc rw,nodev,noexec,nosuid 0 0


My start-up file are as follows:
Code:
rc-update show
                acpid | boot                         
            alsasound | boot                         
            bluetooth |      default                 
             bootmisc | boot                         
                clamd |      default                 
           consolekit |      default                 
                 dbus |      default                 
                devfs |                       sysinit
                dmesg |                       sysinit
           fbcondecor | boot                         
             hostname | boot                         
              hwclock | boot                         
              keymaps | boot                         
            killprocs |              shutdown       
           lm_sensors |      default                 
                local |      default                 
        microcode_ctl | boot                         
              modules | boot                         
             mount-ro |              shutdown       
                 mtab | boot                         
               net.lo |      default                 
               procfs | boot                         
            savecache |              shutdown       
                 swap | boot                         
               sysctl | boot                         
                sysfs |                       sysinit
            syslog-ng |      default                 
       tmpfiles.setup | boot                         
                 udev |                       sysinit
           udev-mount |                       sysinit
                  ufw | boot                         
              urandom | boot                         
           vixie-cron |      default                 
                 wicd |      default                 
                  xdm | boot


My question is do I now have to explicitly enter all of these file systems that currently reside in mtab into my fstab? If I don't will I have issues that I'm not experiencing now?

Any help would be greatly appreciated. TIA

Ciao
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The Doctor
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PostPosted: Wed Jan 23, 2013 11:46 pm    Post subject: Reply with quote

You are fine. Udev is not going to render your system unbootable.

Your fstab looks about like mine from a 2 day old install. I wouldn't worry about that.

You should pay attention to what it says about network naming. This one can be uncomfortable if you are not prepared.
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ulenrich
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PostPosted: Thu Jan 24, 2013 1:12 am    Post subject: Reply with quote

The Doctor wrote:
You should pay attention to what it says about network naming. This one can be uncomfortable if you are not prepared.

What the news could say more clearly:
If you put an all commented out - empty (*)
/etc/udev/rules.d/80-net-name-slot.rules
this overtunes the new network naming feature.
All keeps as used to - no problems.

And you can try later with new names - if you are curious about....

(*)PS: I think udev-197 installed this unfeaturing file for me.
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Ant P.
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PostPosted: Thu Jan 24, 2013 5:13 am    Post subject: Reply with quote

You don't need any new fstab entries - all the commented out ones are handled by initscripts already. The /dev/ ones are done in /etc/init.d/udev-mount.
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ssuominen
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PostPosted: Thu Jan 24, 2013 5:33 am    Post subject: Reply with quote

Ant P. wrote:
You don't need any new fstab entries - all the commented out ones are handled by initscripts already. The /dev/ ones are done in /etc/init.d/udev-mount.


Right. That's why the news item said "possible /dev line" as most people don't have any line there.
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modnaruved
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PostPosted: Thu Jan 24, 2013 6:00 am    Post subject: Reply with quote

After post news and success upgraded too I have same questions on this news advice:

Quote:
- The need of CONFIG_DEVTMPFS=y in the kernel; need to verify the fstype for
possible /dev line in /etc/fstab is devtmpfs (and not, for example, tmpfs)


my kernel devtmpfs settings are:
Code:
CONFIG_DEVTMPFS=y
CONFIG_DEVTMPFS_MOUNT=y


my mount output:
Code:
rootfs on / type rootfs (rw)
/dev/root on / type reiserfs (rw,noatime)
devtmpfs on /dev type devtmpfs (rw,relatime,size=1035092k,nr_inodes=220681,mode=755)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
tmpfs on /run type tmpfs (rw,nosuid,nodev,relatime,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620)
shm on /dev/shm type tmpfs (rw,nosuid,nodev,noexec,relatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,nosuid,nodev,noexec,relatime)
cgroup_root on /sys/fs/cgroup type tmpfs (rw,nosuid,nodev,noexec,relatime,size=10240k,mode=755)
openrc on /sys/fs/cgroup/openrc type cgroup (rw,nosuid,nodev,noexec,relatime,release_agent=/lib/rc/sh/cgroup-release-agent.sh,name=openrc)
cpuset on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cpu on /sys/fs/cgroup/cpu type cgroup (rw,nosuid,nodev,noexec,relatime,cpu)
cpuacct on /sys/fs/cgroup/cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpuacct)
freezer on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
/dev/sda7 on /mnt/data-vol-30 type ext4 (rw,noatime,commit=0)
/dev/sda9 on /mnt/data-vol-57 type ext4 (rw,noatime,commit=0)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)


my fstab content:
Code:
/dev/sda3               /boot           ext2            noauto,noatime  1 2
/dev/sda6               /               reiserfs        noatime         0 1
/dev/sda8               none            swap            sw              0 0
/dev/cdrom              /mnt/cdrom      auto            noauto,ro,user  0 0

# glibc 2.2 and above expects tmpfs to be mounted at /dev/shm for
# POSIX shared memory (shm_open, shm_unlink).
# (tmpfs is a dynamically expandable/shrinkable ramdisk, and will
#  use almost no memory if not populated with files)
shm                     /dev/shm        tmpfs           nodev,nosuid,noexec     0 0

/dev/sda7       /mnt/data-vol-30        ext4    auto,noatime    0       0
/dev/sda9       /mnt/data-vol-57        ext4    auto,noatime    0       0



what need to replace|edit|delete in my fstab for devtmpfs?
just replace tmpfs to devtmpfs or add new line with devtmpfs or remove whole line with shm entry?

These tips form news about line in fstab seems not understandable for me.
I think many users have same questions too.

I would be very grateful for your advice on this matter. Please.

In my opinion if I have CONFIG_DEVTMPFS_MOUNT=y then I dont need add any entry for devtmpfs in my fstab, but
Quote:
possible /dev line in /etc/fstab is devtmpfs (and not, for example, tmpfs)
confuse me, because I have mounted devtmpfs and have also tmpfs in fstab... What should be done with this shm .... tmpfs entry?

Will be great if these details will be reflected in news or in upgrade guide|wiki
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ssuominen
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PostPosted: Thu Jan 24, 2013 6:07 am    Post subject: Reply with quote

CONFIG_DEVTMPFS_MOUNT=y can be used but is not mandatory; the udev-mount init script will take care of mounting it if CONFIG_DEVTMPFS_MOUNT=y is missing
CONFIG_DEVTMPFS=y is the mandatory one
The news item means /dev, not /dev/shm or /dev/porn, just /dev, most people don't have such line at all and that's fine

Details? The news item is accurate enough in my opinion, rest is just bikeshedding
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PostPosted: Thu Jan 24, 2013 6:10 am    Post subject: Reply with quote

ssuominen wrote:
CONFIG_DEVTMPFS_MOUNT=y can be used but is not mandatory; the udev-mount init script will take care of mounting it if CONFIG_DEVTMPFS_MOUNT=y is missing
CONFIG_DEVTMPFS=y is the mandatory one
The news item means /dev, not /dev/shm or /dev/porn, just /dev, most people don't have such line at all and that's fine

Details? The news item is accurate enough in my opinion, rest is just bikeshedding


huh? come again?
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modnaruved
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PostPosted: Thu Jan 24, 2013 6:13 am    Post subject: Reply with quote

ssuominen wrote:
CONFIG_DEVTMPFS_MOUNT=y can be used but is not mandatory; the udev-mount init script will take care of mounting it if CONFIG_DEVTMPFS_MOUNT=y is missing
CONFIG_DEVTMPFS=y is the mandatory one
The news item means /dev, not /dev/shm or /dev/porn, just /dev, most people don't have such line at all and that's fine


thanks and very fast reply :)
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PostPosted: Thu Jan 24, 2013 6:16 am    Post subject: Reply with quote

DaggyStyle wrote:
ssuominen wrote:
CONFIG_DEVTMPFS_MOUNT=y can be used but is not mandatory; the udev-mount init script will take care of mounting it if CONFIG_DEVTMPFS_MOUNT=y is missing
CONFIG_DEVTMPFS=y is the mandatory one
The news item means /dev, not /dev/shm or /dev/porn, just /dev, most people don't have such line at all and that's fine

Details? The news item is accurate enough in my opinion, rest is just bikeshedding


huh? come again?


I mean pr0n of course.
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modnaruved
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PostPosted: Thu Jan 24, 2013 6:22 am    Post subject: Reply with quote

ssuominen wrote:
DaggyStyle wrote:
ssuominen wrote:
CONFIG_DEVTMPFS_MOUNT=y can be used but is not mandatory; the udev-mount init script will take care of mounting it if CONFIG_DEVTMPFS_MOUNT=y is missing
CONFIG_DEVTMPFS=y is the mandatory one
The news item means /dev, not /dev/shm or /dev/porn, just /dev, most people don't have such line at all and that's fine

Details? The news item is accurate enough in my opinion, rest is just bikeshedding


huh? come again?


I mean pr0n of course.


This just mean that udev is very sexy :)
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DaggyStyle
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PostPosted: Thu Jan 24, 2013 8:06 am    Post subject: Reply with quote

devurandom wrote:
ssuominen wrote:
DaggyStyle wrote:
ssuominen wrote:
CONFIG_DEVTMPFS_MOUNT=y can be used but is not mandatory; the udev-mount init script will take care of mounting it if CONFIG_DEVTMPFS_MOUNT=y is missing
CONFIG_DEVTMPFS=y is the mandatory one
The news item means /dev, not /dev/shm or /dev/porn, just /dev, most people don't have such line at all and that's fine

Details? The news item is accurate enough in my opinion, rest is just bikeshedding


huh? come again?


I mean pr0n of course.


This just mean that udev is very sexy :)


udev is very sexy as Lennard Pottering is very sexy.
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Odysseus
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PostPosted: Thu Jan 24, 2013 9:37 am    Post subject: Reply with quote

Thanks to all for the rapid responses! I just got home from work and was quite pleasantly surprised to see so many of them. This is one of the reasons I love Gentoo, the community is knowledgeable and helpful (provided it isn't an obvious question that's been answered numerous times) :wink: :wink:

Anyhow I feel better now that my system remains usable and relatively stable (as stable as one can be when running ~amd64 and other bits of leading edge software like gcc-4.7.2 and glibc-2.17). :lol: :lol:

I think I'll wait a bit before tackling the network naming stuff until it's been in use for a while and I'm convinced the applications in my system are up to the task.

Thanks again everyone!

Ciao
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