simultaneous dirinstalls leave first /tmp/tmp.X and /tmp/tmp.X/dev mounted (patch)

[andrew bezella]

hello -

we're using fai 5.0.3 and have been seeing a problem when there are two
or more simultaneous dirinstalls taking place on a ubuntu xenial/16.04
host.  i haven't tested with newer versions of fai, but it looks like
/usr/lib/fai/updatebase hasn't changed that much between then and now. 

(apologies in advance for the long lines...)
 
the problem appears to be with the bind mount of /dev into the
$FAI_ROOT/dev chroot and the subsequent devpts mount at
$FAI_ROOT/dev/pts.  on our systems, this results in a shared(?) devpts
filesystem mounted repeatedly on the host's /dev/pts as well as
multiple times in the first dirinstall (/tmp/tmp.9TKUTDClPW below, both
dirinstalls in process):
devpts                                                              on  /dev/pts                                type  devpts      (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
/dev/mapper/xenvg-beff2349--8d77--4ef3--9988--23d7ca0e2461.disk0-1  on  /tmp/tmp.9TKUTDClPW                     type  ext4        (rw,relatime,block_validity,delalloc,barrier,user_xattr,acl)
/dev/mapper/xenvg-c10d187e--9fd6--4eb6--a916--19ade0447915.disk0-1  on  /tmp/tmp.OTjBmSXukS                     type  ext4        (rw,relatime,block_validity,delalloc,barrier,user_xattr,acl)
tmpfs                                                               on  /tmp/tmp.9TKUTDClPW/var/lib/dpkg        type  tmpfs       (rw,noatime)
tmpfs                                                               on  /tmp/tmp.OTjBmSXukS/var/lib/dpkg        type  tmpfs       (rw,noatime)
proc                                                                on  /tmp/tmp.9TKUTDClPW/proc                type  proc        (rw,relatime)
sysfs                                                               on  /tmp/tmp.9TKUTDClPW/sys                 type  sysfs       (rw,relatime)
udev                                                                on  /tmp/tmp.9TKUTDClPW/dev                 type  devtmpfs    (rw,nosuid,relatime,size=12305280k,nr_inodes=3076320,mode=755)
devpts                                                              on  /tmp/tmp.9TKUTDClPW/dev/pts             type  devpts      (rw,relatime,mode=600,ptmxmode=000)
devpts                                                              on  /dev/pts                                type  devpts      (rw,relatime,mode=600,ptmxmode=000)
proc                                                                on  /tmp/tmp.OTjBmSXukS/proc                type  proc        (rw,relatime)
sysfs                                                               on  /tmp/tmp.OTjBmSXukS/sys                 type  sysfs       (rw,relatime)
udev                                                                on  /tmp/tmp.OTjBmSXukS/dev                 type  devtmpfs    (rw,nosuid,relatime,size=12305280k,nr_inodes=3076320,mode=755)
devpts                                                              on  /tmp/tmp.OTjBmSXukS/dev/pts             type  devpts      (rw,relatime,mode=600,ptmxmode=000)
devpts                                                              on  /dev/pts                                type  devpts      (rw,relatime,mode=600,ptmxmode=000)
devpts                                                              on  /tmp/tmp.9TKUTDClPW/dev/pts             type  devpts      (rw,relatime,mode=600,ptmxmode=000)

when that first dirinstall has completed, it tries to umount
everything.  however, this fails since there is the
extraneous /tmp/tmp.9TKUTDClPW/dev/pts that is apparently still in use
until the second dirinstall also completes (i'm unclear on the exact
details of how/why).  we're left with the first dirinstall error'ing
out:
The dirinstall took 369 seconds.
umount: /tmp/tmp.9TKUTDClPW/dev: target is busy
        (In some cases useful info about processes that
         use the device is found by lsof(8) or fuser(1).)
Source hook: savelog.LAST.sh
ERRORS found in log files. See /var/log/fai/instance4.us.archive.org/dirinstall-20180706_233705/error.log
 
and its root and /dev left in place:
/dev/mapper/xenvg-beff2349--8d77--4ef3--9988--23d7ca0e2461.disk0-1  on  /tmp/tmp.9TKUTDClPW                     type  ext4        (rw,relatime,block_validity,delalloc,barrier,user_xattr,acl)
udev                                                                on  /tmp/tmp.9TKUTDClPW/dev                 type  devtmpfs    (rw,nosuid,relatime,size=12305280k,nr_inodes=3076320,mode=755)

i looked at how the schroot package avoids this and it uses `mount --
private`.  the attached patch applies that option to the $FAI_ROOT/dev
and $FAI_ROOT/dev/pts mounts set up via /usr/lib/fai/updatebase and
clears up this dirinstall problem.  i'll be testing it early next week
to ensure it doesn't introduce any issues on a netbooted install; if
that works (and barring feedback/concerns) i'll then submit an mr to
the fai repo.

thanks...

	andy

-- 
andrew bezella <abezella at archive.org>
internet archive
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