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lkvm: cannot run rkt from systemd-run because $HOME undefined #1393

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alban opened this issue Sep 14, 2015 · 11 comments
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lkvm: cannot run rkt from systemd-run because $HOME undefined #1393

alban opened this issue Sep 14, 2015 · 11 comments
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depends-on/external kind/bug technology/kvm
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vfuture

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@alban
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alban commented Sep 14, 2015 

$ sudo systemd-run -t /home/alban/go/src/github.com/coreos/rkt/build-rkt-0.8.0+git/bin/rkt --debug --insecure-skip-verify run --private-net=default --volume volume-data,kind=host,source=/tmp/redis --stage1-image=/home/alban/go/src/github.com/coreos/rkt/build-rkt-0.8.0+git/bin/stage1.aci --mds-register=false --local docker://redis
...
  # lkvm run -k stage1/rootfs/bzImage -m 128 -c 1 --name rkt-431edd16-6f75-41d3-bf4f-3584ad4af3ca
bind: No such file or directory
  Error: Failed adding socket to epoll
  Warning: Failed init: kvm_ipc__init

  Fatal: Initialisation failed

The same command executed directly (without systemd-run) works fine. When adding strace -e bind,open,stat,execve -f -s 512, it shows:

bind(6, {sa_family=AF_LOCAL, sun_path="/var/lib/rkt/pods/run/6c99d0ab-a0eb-4bb0-ae02-aec1e6f9bffc/(null)/rkt-6c99d0ab-a0eb-4bb0-ae02-aec1e6f9bffc."}, 109) = -1 ENOENT (No such file or directory)

The (null) in the socket path comes from kvm-ipc.c#44:

snprintf(full_name, sizeof(full_name), "%s/%s%s",
     kvm__get_dir(), kvm->cfg.guest_name, KVM_SOCK_SUFFIX);

The problem is that kvm__get_dir() is using $HOME and that variable is undefined. Moreover, the way lkvm uses realpath will make it set the directory to an uninitialized value from the stack:
main.c#16

Workaround: define $HOME when using systemd-run

$ sudo systemd-run -t --setenv=HOME=/root ...

Alternative workaround: use --uid=0, and $HOME will be implicitly defined.

$ sudo systemd-run --uid=0 -t --setenv=HOME=/root ...
alban added a commit to alban/rkt that referenced this issue Sep 14, 2015
@alban
lkvm: don't rely on $HOME
bfc80b9 
When rkt is started via systemd-run, $HOME might not be defined.

Symptoms:
|bind: No such file or directory
|  Error: Failed adding socket to epoll
|  Warning: Failed init: kvm_ipc__init
|
|  Fatal: Initialisation failed

Fix rkt#1393
@yifan-gu yifan-gu mentioned this issue Sep 14, 2015
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@alban alban mentioned this issue Sep 14, 2015
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@jonboulle
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great find!

alban added a commit to alban/rkt that referenced this issue Sep 15, 2015
@alban
doc: rkt with systemd: lkvm: workaround for missing $HOME
8418691 
Running the lkvm flavor of rkt in systemd does not currently work if
$HOME is not defined: see rkt#1393

It should be fixed in lkvm upstream, but meanwhile, mention the
workaround in the documentation.
@alban alban mentioned this issue Sep 15, 2015
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alban added a commit to alban/rkt that referenced this issue Sep 16, 2015
@alban
doc: lkvm: troubleshooting for missing $HOME
2b05318 
More documentation in addition to rkt#1401

Running the lkvm flavor of rkt in systemd does not currently work if
$HOME is not defined: see rkt#1393

It should be fixed in lkvm upstream, but meanwhile, mention the
workaround in the documentation.
alban added a commit to alban/rkt that referenced this issue Sep 16, 2015
@alban
doc: lkvm: troubleshooting for missing $HOME
97b2234 
More documentation in addition to rkt#1401

Running the lkvm flavor of rkt in systemd does not currently work if
$HOME is not defined: see rkt#1393

It should be fixed in lkvm upstream, but meanwhile, mention the
workaround in the documentation.
@alban alban mentioned this issue Sep 16, 2015
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@jonboulle
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Workaround documented: #1401

Proper solution will be in upstream patch: http://thread.gmane.org/gmane.comp.emulators.kvm.devel/140459

@alban
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alban commented Sep 18, 2015

I wonder if instead of documenting the workaround, we should add some code in stage1/init/init.go to set $HOME if it is not already set. That would be a better workaround for the user while waiting for upstream.

@jonboulle
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You mean just for lkvm?

On Fri, Sep 18, 2015 at 10:09 AM, Alban Crequy notifications@github.com
wrote:

I wonder if instead of documenting the workaround, we should add some code
in stage1/init/init.go to set $HOME if it is not already set. That would
be a better workaround for the user while waiting for upstream.

—
Reply to this email directly or view it on GitHub
#1393 (comment).

@alban
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alban commented Sep 18, 2015

Yes, just for lkvm.

@jonboulle
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Seems reasonable.

On Fri, Sep 18, 2015 at 11:38 AM, Alban Crequy notifications@github.com
wrote:

Yes, just for lkvm.

—
Reply to this email directly or view it on GitHub
#1393 (comment).

@jellonek
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As for temporary solution - seems very reasonable.

alban added a commit to alban/rkt that referenced this issue Sep 20, 2015
@alban
lkvm: make sure $HOME is defined before running lkvm
83f94ca 
kvmtool currently does not work when $HOME is not defined. When started
by a systemd unit file (or by systemd-run), $HOME is typically
undefined, unless "User=" (or resp. "--uid=") is given.

Instead of asking users to work around the issue with "User=" or
"--uid=", just define that variable in rkt before calling lkvm.

This could be removed when this gets fixed in lkvm upstream.

Issue described in rkt#1393
@alban alban mentioned this issue Sep 20, 2015
Merged
alban added a commit to alban/rkt that referenced this issue Sep 21, 2015
@alban
lkvm: make sure $HOME is defined before running lkvm
c43be2e 
kvmtool currently does not work when $HOME is not defined. When started
by a systemd unit file (or by systemd-run), $HOME is typically
undefined, unless "User=" (or resp. "--uid=") is given.

Instead of asking users to work around the issue with "User=" or
"--uid=", just define that variable in rkt before calling lkvm.

This could be removed when this gets fixed in lkvm upstream.

Issue described in rkt#1393
@jonboulle
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@alban @jellonek did this ever land upstream?

@jonboulle jonboulle added this to the vfuture milestone Jan 15, 2016
@alban
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alban commented Jan 18, 2016

No, this didn't land upstream. But since #1447 is merged, rkt works fine.

@jellonek
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Upstream topic died somewhere around September so #1447 should be treated as solution and not as a workaround.

IMO this issue should be closed.

@alban
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alban commented Jan 18, 2016

Ok, closing.

For the record, #1447 was merged into v0.9.0.

@alban alban closed this as completed Jan 18, 2016
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