[Bug 607636] [NEW] chardev: opening backend "pty" failed

[Daniel Adolfsson]

Public bug reported:

I'm unable to start qemu virtual machine because of the following error:

error: Failed to start domain test
error: internal error unable to start guest: chardev: opening backend "pty" failed

The reason I'm posting this on libvirtd, is because I'm able to run the
exact same command (as printed in the log file) manually - and it works.
I believe qemu bails because openpty() fails - as a direct result of
chown() failing.

Both qemu and libvirtd is running as root - and apparmor is not active.

This could be a capabilies issue.

(from strace)
[pid  3058] getuid()                    = 0
....
[pid  3058] chown("/dev/pts/3", 0, 5)   = -1 EPERM (Operation not permitted)

(from /proc/[pid of libvirtd]/status)
Uid:    0       0       0       0
Gid:    0       0       0       0
CapPrm: ffffffffffffffff
CapEff: ffffffffffffffff
CapBnd: ffffffffffffffff

(from /proc/[pid of qemu]/status)
Uid:    0       0       0       0
Gid:    0       0       0       0
CapPrm: fffffffc00000000
CapEff: fffffffc00000000
CapBnd: fffffffc00000000

(ls -la /dev/pts)
drwxr-xr-x  2 root  root      0 2010-04-19 09:30 .
c---------  1 root  root   5, 2 2010-07-19 13:55 ptmx

(mount)
none on /dev type devtmpfs (rw,mode=0755)
none on /dev/pts type devpts (rw,mode=620,mode=620)

(qemu-log)
LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/sbin:/sbin:/bin /usr/bin/kvm -S -M pc-0.12 -enable-kvm -m 512 -smp 1 -name ferret -uuid 1e2e6382-904d-11df-9ea9-0040d0c0493e -nographic -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/ferret.monitor,server,nowait -monitor chardev:monitor -boot c -drive file=/dev/mapper/vg0-lv3,if=virtio,index=0,boot=on -net nic,macaddr=52:54:00:43:4a:33,vlan=0,model=virtio,name=virtio.0 -net tap,ifname=tap0,script=/bin/true,vlan=0,name=tap.0 -chardev pty,id=serial0 -serial chardev:serial0 -parallel none -usb

Any ideas?

** Affects: libvirt (Ubuntu)
     Importance: Undecided
         Status: New

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chardev: opening backend "pty" failed
https://bugs.launchpad.net/bugs/607636
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