[FS#135] sysupgrade broken on x86 generic?

[LEDE Bugs]

The following task has a new comment added:

FS#135 - sysupgrade broken on x86 generic?
User who did this - Jo-Philipp Wich (jow-)

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I just tried a sysupgrade using a current LEDE x86/generic snapshot and encountered no issues.

Commandline used for testing:
sudo qemu-system-i386 -net nic,model=e1000 -net tap -hda dummy.img -hdb lede-x86-generic-combined-ext4.img -boot menu=on

Sysupgrade log:
root at lede:~# sysupgrade /tmp/lede-x86-generic-combined-ext4.img.gz 
Saving config files...
Sending TERM to remaining processes ... logd netifd odhcpd dnsmasq ntpd ubusd askfirst 
Sending KILL to remaining processes ... askfirst 
Switching to ramdisk...
Performing system upgrade...
Reading partition table from bootdisk...
0+1 records in
0+1 records out
Reading partition table from image...
Writing image to /dev/sdb1...
8192+0 records in
4+0 records out
Writing image to /dev/sdb2...
524288+0 records in
256+0 records out
Writing new UUID to /dev/sdb...
4+0 records in
4+0 records out
Upgrade completed
Rebooting system...
umount: can't unmount /dev/pts: Resource busy
umount: can't unmount /dev: Resource busy
packet_write_wait: Connection to 192.168.1.1 port 22: Broken pipe
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=135#comment585