Hi Jouni,
thank you for your report and your help to make Ubuntu better.
I rejected the suggestion that nothing happens and instead tried to reproduce
to understand the issue better :-)
# I have used screen with and without -q, just with -q it is more
readable and needs less returns
# works as my own user
$ screen
# becoming root via sudo, then screen still works
$ sudo su -
$ screen
# from there become another user, still works
$ su otheruser -
$ screen
I have no local root login atm, so for reproduction might I ask how you get
your initial shell?
Do you have a remote login with root login allowed or is this a local root
logon?
As fallback I created a local KVM Guest, and enabled root login there:
$uvt-kvm create --memory 2048 --cpu 4 --disk 8 --password=ubuntu
zesty-test-screen release=zesty arch=amd64 label=daily
# there I then enabled root login in /etc/sshd_config
$ ssh root@kvmguest
$ su ubuntu
$ screen
Here I was then able to reproduce your case.
"Cannot open your terminal '/dev/pts/0' - please check."
And it makes sense as the current local /dev/pts/0 is owned by root.
As a workaround there you can e.g. run
$ script /dev/null
# This will create a /dev/pts/* of your user that screen can reuse, not a fix
but a workaround
I've found that some directly wrap this up as
$ /usr/bin/script -q -c "/usr/bin/screen ${*}" /dev/null
So overall, working with a main root login should never be the default for
security reasons.
If you do so you might end up with some extra hickups and IMHO that is one of
them.
You can create a case of this issue without root login, by switching around
users with su.
But the root cause always is that the current user can't access /dev/pty/* due
to being different user than the initial terminal creating one.
Since there is a workaround for it available and easily to be found on
the internet (now one more with this bug) I think it is not a high
severity.
Also I don't think screen should create a different pty for his own user on its
own.
I'd more consider this (not to allocate a new tty a feature/limitation) of su.
That said I'd rate this as wishlist issue or almost a Won't Fix - but
I'd leave it open to you or others to comment if this is more severe
than I think.
** Changed in: screen (Ubuntu)
Status: New => Confirmed
** Changed in: screen (Ubuntu)
Importance: Undecided => Wishlist
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https://bugs.launchpad.net/bugs/1644636
Title:
Cannot open your terminal /dev/pts/X - please check
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