Socob's questions

I’ve installed the ibus-table-latex package via APT and it works fine. However, I don’t see a way to re-bind (or disable) some of the triggers (backslash \, _, ^) that open the “candidate list”. In particular, I’d like to get rid of ^ and _ doing anything special.

In the input method setup, I’ve found this “Key bindings” page:

but these triggers are nowhere in that list.

More generally (but perhaps this warrants a separate question), is there any documentation for ibus-table-latex that would explain how or whether these can be changed? The only things I’ve found are

• The ibus-table-others GitHub page
• A short sentence on the IBus Wikipedia page
• The “About” button gives this link (there’s also this one with identical content), which is devoid of any information

After an apt updgrade, I ran into some boot issues involving systemd dependency cycles (like in zfs-linux#1875577). So, since I’m running 20.10 on ZFS (with encryption), I decided to revert the system state using the GRUB ZFS history entries. However, this apparently caused me to run into this bug with the rpool/ROOT/ubuntu_ dataset (see this question), and so I still can’t boot my system. Moreover, now mounting /var/lib/NetworkManager and /var/lib/apt was failing during the boot process.

I tried to see if I can investigate by mounting the ZFS file system from a live USB session:

zpool export -a
zpool import -N -R /mnt rpool
zpool import -N -R /mnt bpool
cryptsetup open --type luks /dev/zvol/rpool/keystore keystore
mkdir -p /run/keystore/rpool
mount /dev/mapper/keystore /run/keystore/rpool
zfs load-key -a
zfs mount rpool/ROOT/ubuntu_<UUID>
zfs mount bpool/BOOT/ubuntu_<UUID>
zfs mount -a

The result of zfs mount -a showed similar errors as while booting:

cannot mount '/mnt/var/lib/NetworkManager': failed to create mountpoint
cannot mount '/mnt/var/lib/apt': failed to create mountpoint

Trying to see what’s going on, I get these strange question marks in ls for /mnt/var/lib/NetworkManager and /mnt/var/lib/apt, but also access errors for these paths.

$ ls -ahl /mnt/var/lib/
ls: cannot access '/mnt/var/lib/NetworkManager': No such file or directory
ls: cannot access '/mnt/var/lib/apt': No such file or directory
total 718K
drwxr-xr-x 80 root          root          80 Nov 18 00:53 .
drwxr-xr-x 16 root          root          18 Oct 22 14:17 ..
drwxr-xr-x  4 root          root           4 Oct 22 14:01 AccountsService
drwxr-xr-x  2 root          root           2 Jan 31  2019 acpi-support
drwxr-xr-x  2 root          root           3 Dec  1 13:38 alsa
drwxr-xr-x  5 root          root           5 Nov 18 00:54 apache2
drwxr-xr-x  4 root          root           4 Dec  1 11:25 app-info
d?????????  ? ?             ?              ?            ? apt
drwxr-xr-x  2 root          root           4 Nov 19 21:58 aptitude
drwxr-xr-x  2 root          root          27 Oct 22 14:12 aspell
drwxr-xr-x  2 avahi-autoipd avahi-autoipd  2 Oct 22 14:09 avahi-autoipd
drwxr-xr-x  2 root          root           5 Nov 15 23:06 binfmts
drwxr-xr-x  3 root          root           3 Nov 15 13:40 bluetooth
drwxr-xr-x  2 root          root           2 Jun 16 14:01 boltd
drwxrwxrwt  2 root          root           2 Jul 27 15:38 BrlAPI
drwxr-xr-x  4 colord        colord         6 Nov 15 15:01 colord
drwxr-xr-x  2 root          root           4 Dec  1 11:25 command-not-found
drwxr-xr-x  2 root          root           3 Nov 15 15:01 dbus
drwxr-xr-x  2 root          root           2 Aug 12 09:33 dhcp
drwxr-xr-x  5 root          root           5 Oct 22 14:08 dictionaries-common
drwxr-xr-x  3 root          root           4 Dec  1 12:05 dkms
drwxr-xr-x  7 root          root          18 Dec  1 12:06 dpkg
drwxr-xr-x  3 root          root           3 Oct 22 14:02 emacsen-common
drwxr-xr-x  2 root          root           2 Apr 16  2020 fprint
drwxr-xr-x  6 root          root           7 Nov 15 23:05 fwupd
drwxr-xr-x  5 gdm           gdm            6 Dec  1 13:30 gdm3
drwxr-xr-x  3 root          root           3 Nov 15 22:59 gems
drwxr-xr-x  2 geoclue       geoclue        2 Feb 28  2020 geoclue
drwxr-xr-x  4 root          root           4 Oct 22 14:03 ghostscript
drwxr-xr-x  2 root          root           2 Jun  9 20:50 git
drwxr-xr-x  4 root          root           4 Oct 22 14:04 grub
drwxr-xr-x  2 root          root           2 Jun 22 10:09 hp
drwxr-xr-x  2 root          root           6 Nov 25 11:32 initramfs-tools
drwxr-xr-x  2 root          root           3 Oct 22 14:02 ispell
drwxr-xr-x  3 root          root           3 Oct 22 14:05 libreoffice
drwxr-xr-x  3 root          root           3 Nov 15 22:59 libxml-sax-perl
drwxr-xr-x  3 root          root           3 Oct 22 14:12 locales
drwxr-xr-x  2 root          root           3 Nov 30 23:00 logrotate
drwxr-xr-x  2 root          root           3 Oct 22 14:10 man-db
drwxr-xr-x  2 root          root           2 Oct 16 15:40 misc
d?????????  ? ?             ?              ?            ? NetworkManager
drwxr-xr-x  3 root          root           3 Oct 22 14:10 openvpn
drwxr-xr-x  2 root          root           2 Dec  1 12:55 os-prober
drwxr-xr-x  2 root          root           3 Dec  1 13:31 PackageKit
drwxr-xr-x  2 root          root           8 Nov 19 21:57 pam
drwxr-xr-x  4 root          root           4 Nov 15 23:35 php
drwxr-xr-x  2 root          root           3 Nov 15 15:01 plymouth
drwx------  3 root          root           3 Oct 22 13:59 polkit-1
drwx------  2 root          root           2 Oct 22 13:59 private
drwxr-xr-x  2 root          root           3 Oct 22 13:59 python
drwxr-xr-x  2 root          root           2 Sep  8 18:15 realmd
drwxr-xr-x  2 root          root           4 Nov 19 21:57 sgml-base
drwxr-xr-x  3 root          root           5 Nov 15 15:18 shim-signed
drwxr-xr-x 24 root          root          26 Dec  1 13:30 snapd
drwxr-xr-x  2 root          root           2 Aug  6 15:42 snmp
drwxr-xr-x 10 root          root          10 Oct 22 14:09 sss
drwxr-xr-x  3 root          root           3 Oct 22 13:59 sudo
drwxr-xr-x  2 root          root           2 Feb 28  2020 synaptic
drwxr-xr-x 12 root          root          13 Nov 15 15:01 systemd
drwxr-xr-x  5 root          root           5 Nov 15 22:59 tex-common
drwxr-xr-x  9 root          root          16 Nov 18 00:54 texmf
drwx--S---  3           127           135  9 Dec  1 13:38 tor
drwxr-xr-x  2 tss           tss            2 Dec  3  2019 tpm
drwxr-xr-x  2 root          root           3 Nov 15 13:46 ubiquity
drwxr-xr-x  2 root          root           2 Sep  1 17:14 ubuntu-advantage
drwxr-xr-x  2 root          root           3 Nov 15 15:01 ubuntu-drivers-common
drwxr-xr-x  2 root          root           2 Nov 28 13:17 ubuntu-release-upgrader
drwxr-xr-x  3 root          root          21 Nov 18 01:28 ucf
drwx------  2 root          root           3 Dec  1 13:30 udisks2
drwxr-xr-x  2 root          root           2 Aug  5 12:03 unattended-upgrades
drwxr-xr-x  2 root          root           2 Jul 23 19:50 update-manager
drwxr-xr-x  4 root          root           6 Dec  1 12:06 update-notifier
drwxr-xr-x  2 root          root           6 Dec  1 13:05 upower
drwxr-xr-x  2 root          root           2 Jul 27 16:30 usb_modeswitch
drwxr-xr-x  2 root          root           3 Oct 22 14:02 usbutils
drwxr-xr-x  3 root          root           3 Oct 22 13:59 vim
drwxr-xr-x  2 root          root           3 Dec  1 13:30 whoopsie
drwxr-xr-x  2 root          root           3 Oct 22 14:10 xfonts
drwxr-xr-x  2 root          root           3 Oct 22 14:04 xkb
drwxr-xr-x  2 root          root           6 Oct 22 14:11 xml-core

Trying to access or delete these paths claims that no such files exist, while trying to mkdir claims that the files do already exist! (This is why the mount point cannot be created.)

$ ls /mnt/var/lib/NetworkManager
ls: cannot access '/mnt/var/lib/NetworkManager': No such file or directory
$ rm /mnt/var/lib/NetworkManager
rm: cannot remove '/mnt/var/lib/NetworkManager': No such file or directory
$ rmdir /mnt/var/lib/NetworkManager
rmdir: failed to remove '/mnt/var/lib/NetworkManager': No such file or directory
$ mkdir /mnt/var/lib/NetworkManager
mkdir: cannot create directory ‘/mnt/var/lib/NetworkManager’: File exists

What happened here? How can I get rid of these path entries?

In previous versions of Ubuntu, one could press Ctrl-Shift-E in any text input area to activate the “Emoji Choice” popup – see, for example, these answers to “What does [Ctrl] + [Shift] + [e] do, while typing text?” or “How to insert an emoji into a text in Ubuntu 18.04 and later?”. This has several advantages over the “Insert Emoji” (Ctrl-.) method available e. g. in gedit, the main ones being

• It works with any text input area, not just specific programs like gedit.
• It not only allows searching and choosing emoji, but any Unicode character.

However, when I try pressing Ctrl-Shift-E in Ubuntu 20.10 (e. g. in gedit or Firefox), nothing happens. I still see the shortcut showing up when running ibus-setup:

and in the dconf editor:

Was the keyboard shortcut for the “Emoji Choice” popup removed? And how can I get it working again?

In order not to clutter the list of my recently used files, e. g. when looking through a bunch of media files, I’d like to exclude some file types or paths from being included in the file history (e. g. exclude all .jpg files, or, if that’s not possible, at least exclude individual paths like ~/Pictures or ~/Music to have a similar effect).

I know that the list of recently used files is stored in ~/.local/share/recently-used.xbel, but how can I configure what is written there? The only relevant option seems to be in “Settings → Privacy → File History & Trash”, where file history can be disabled entirely. However, I still want to have a file history, just with some more configuration. I remember that, for example, in the Unity days, it was possible to exclude certain file types (like “Images”, “Videos” or “Documents”) from being tracked in this way – did this functionality disappear?

I installed Ubuntu 20.10 on a new machine with the ZFS option, i. e. both /boot and the root file system are on ZFS. However, I need the newer kernel version 5.9 for hardware support, which I installed using the mainline kernel PPA. Unfortunately, the version of ZFS included in Ubuntu 20.10 (v0.8.4) doesn’t work with Linux v5.9 kernels (building the kernel module fails).

This leads to quite the predicament: How can I use both the required newer kernel version and ZFS (of course, including full functionality, such as ZSys)?

• I’ve tried building and installing ZFS from source. However, the .deb packages created when building ZFS from source are incompatible with Ubuntu’s packages, and thus anything that depends on the Ubuntu packages (like ZSys!) falls victim to the package conflicts and has to be removed/cannot be installed.

• Due to these problems, I noticed that current Debian bullseye (testing) has newer packages with version 0.8.5 of ZFS (which is compatible with Linux v5.9), and the packaging scheme looks compatible with the one in Ubuntu. So I tried upgrading to these packages, and building the kernel modules for my mainline 5.9.8 kernel did indeed succeed. However, on boot, this fails to mount the ZFS file system (even with the normal 5.8 Ubuntu kernel):

  Command: mount -o zfsutil -t zfs rpool/ROOT/ubuntu_682y7z /root//
  Message: filesystem 'rpool/ROOT/ubuntu_682y7z' can not be mounted: Permission denied
  

So, now I’m stuck. What is the most robust way of running a mainline kernel which also requires upgrading ZFS? I did consider building a custom 5.9 kernel with built-in ZFS support, but wouldn’t the ZFS version in my kernel then conflict with the installed Ubuntu packages, which use an older version of ZFS?

I wanted to change the default behavior of the less command, so I added the following to ~/.profile:

LESS="$LESS -x4"
export LESS

However, the mere presence of a set LESS environment variable seems to change the behavior of the less command, since this now causes git diff to show me raw escape sequences.

More generally, the output of

LESS='' git diff

and

unset LESS; git diff

differs. What is the difference between having LESS unset and LESS set to an empty value (besides the former apparently implying -R)?

Some packages in the Ubuntu repositories provide pre-compiled binaries of shared libraries (*.so). For example, the package fftw2 provides the FFTW library (version 2), including the MPI-related library files /usr/lib/libfftw_mpi.so.2 and /usr/lib/librfftw_mpi.so.2. This evokes the question of which of the numerous MPI libraries these files are actually linked against. On my system (amd64), ldd /usr/lib/libfftw_mpi.so.2 shows

  linux-vdso.so.1 (0x00007ffd80ba4000)
  libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f2c3fe22000)
  libmpi.so.20 => /usr/lib/x86_64-linux-gnu/libmpi.so.20 (0x00007f2c3fb30000)
  […]

So they seem to point to Open MPI, whose files are called libmpi.so on Ubuntu.

I have found the mpi-default-dev metapackage, whose description is

This metapackage depends on the development files of the recommended MPI implementation for each platform, currently Open MPI on all of the platforms where it exists, and MPICH on the others. The package which this depends on has alternatives links for the shared libraries libmpi and libmpi++, and for compilers mpicc, mpic++/mpicxx/mpiCC, mpif77 and mpi90 and their manpages.

And indeed, on amd64, this pulls in Open MPI. However, does that mean that all libraries using MPI in the Ubuntu repositories are necessarily compiled with/linked against Open MPI?

I’m trying to set up an Ubuntu 18.04 machine and joining it to an Active Directory domain. Previously (e. g. on Ubuntu 17.10) I could do

# kinit -kt /path/to/keytab my_username
# realm join ad.example.com

However, with Ubuntu 18.04, it seems that the realm command doesn’t see the Kerberos ticket:

# kinit -kt /path/to/keytab my_username
# realm join --verbose ad.example.com
 * Resolving: _ldap._tcp.ad.example.com
 * Performing LDAP DSE lookup on: 10.A.B.150
 * Performing LDAP DSE lookup on: 10.C.D.131
 * Successfully discovered: ad.example.com
Password for Administrator:
 * Unconditionally checking packages
 * Resolving required packages
 * LANG=C /usr/sbin/adcli join --verbose --domain ad.example.com --domain-realm AD.EXAMPLE.COM --domain-controller 10.A.B.150 --login-type user --login-user Administrator --stdin-password
 * Using domain name: ad.example.com
 * Calculated computer account name from fqdn: PCTEST
 * Using domain realm: ad.example.com
 * Sending netlogon pings to domain controller: cldap://10.A.B.150
 * Received NetLogon info from: ADS2.ad.example.com
 * Wrote out krb5.conf snippet to /var/cache/realmd/adcli-krb5-liolnd/krb5.d/adcli-krb5-conf-032njz
 ! Couldn't authenticate as: [email protected]: Preauthentication failed
adcli: couldn't connect to ad.example.com domain: Couldn't authenticate as: [email protected]: Preauthentication failed
 ! Failed to join the domain

What could be happening here? Is there something obvious I’m missing (e. g. some package is not installed)?

With Ubuntu 17.10, Okular (installed through the Ubuntu repositories, i. e. apt install okular) seems to work a lot worse than in previous versions. This is both on Wayland and on the X session. Here is a screenshot:

For example: As you can see, only the item “Contents” in the left sidebar has an icon. The other ones (“Thumbnails”, “Reviews”, “Bookmarks”) should have icons as well (see e. g. this screenshot).

Moreover, when I open Okular from the Terminal, I get a bunch of output:

inotify_add_watch("/home/user/.config/ibus/bus/9f77c45ee0ec4b6a89aaaa7669ff56c1-unix-0") failed: "No space left on device"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/16/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/22/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/24/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/32/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/48/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/64/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/128/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/16/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/22/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/24/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/32/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/48/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/64/"
Invalid Context= "stock" line for icon theme:  "/usr/share/icons/ubuntu-mono-dark/stock/128/"

The messages about the icon theme might be related to the missing icons. The first line apparently means that the limit of inotify watches has been reached – why is that happening?

Lastly, the UI theme looks nothing like other applications in Ubuntu (I guess this is a problem with Qt applications in general?) – look at the scroll bars, for example. I suppose this has to do with the move back to GNOME? It used to be much better in Ubuntu versions before 17.10.

Is there any way to fix/work around these issues?

As another data point, there is the question “Okular instances do not group under single icon in desktop dock on Ubuntu 17.10”, but that already has a solution in the link.

This is related to questions like “How do I run executable scripts in Nautilus?” or “How to execute a script just by double clicking like .EXE files in Windows?”.

I would also like to have shell scripts run if they are opened in the file manager (Nautilus), but the usual setting (org ➤ gnome ➤ nautilus ➤ preferences ➤ executable-text-activation) is not fine-grained enough for my purposes. If I set it to ask or launch, any text file with the executable bit set will (ask to) be launched as a script. This is problematic because we have some scripts on a file system (CIFS) which does not support Unix permissions (owner/group, rwx). That means that when I mount this file system, I can only either

1. set all files as executable (including, of course, any text files) or
2. set all files as not executable.

Consequently, when I open any text file (*.txt/MIME type text/plain), even if it has no script-related contents, the file will still (ask to) be executed. This is really annoying and irritating for inexperienced users – of course I don’t want to “run” a text/plain file.

Is there a way to make Nautilus treat only actual shell scripts (e. g. MIME type application/x-shellscript) as executable scripts?

On Ubuntu 14.10, I'm connecting to the same VPN service using either OpenConnect (through the network-manager-openconnect(-gnome) packages or the Cisco AnyConnect Client. Using the AnyConnect client, I have had no problems, while OpenConnect gives me strange connection issues (but only with some programs).

I suspect the problems are caused by the fact that the VPN provider does not support IPv6. Connecting to http://whatismyipv6.com using the AnyConnect client, an IPv4 address is displayed, while using OpenConnect, my (non-VPN!) IPv6 address is shown. The AnyConnect client seems to force all connections through the VPN, even if IPv6 is unavailable. The following is a screenshot of the Statistics -> Details page in the AnyConnect client:

How can I achieve the same using OpenConnect? In Network Manager, under "Edit connection", there is an "IPv6 settings" tab, but the only relevant setting seems to be "Method" with the options "Ignore", "Automatic (VPN)" and "Automatic (VPN) addresses only" – I don't know what the difference between them is, but none of them seem to do what I want. Is the --disable-ipv6 flag that can be given to openconnect related? How would one use that in Network Manager?

Note: I have seen this question about disabling IPv6 with OpenVPN, but the answer given there is unsatisfactory – I don't want to manually and globally enable/disable IPv6 every time I connect to or disconnect from the VPN.

If you open a PDF file in Okular and choose the menu entry "File -> Properties", a list of the current file's various properties is displayed. Among them is the entry

Optimized: <Yes|No>

What does it mean for a PDF file to be "optimized"? I haven't been able to find any documentation on this.