anx's questions

If someone/something shuts down the machine I am logged in to via ssh, I usually get just

Shared connection to 2001:db8::1 closed.

I would like to distinguish this from local or network issues:

Power button (/dev/input/..) pressed, shutting down now.
Critical battery action: shutting down now.
Immediate shutdown initiated by user betty, no wall message provided.

Where can I hook into systemd to enable a detailed broadcast while handling power buttons?

Partial solutions:

• A systemd unit hooked to run before sshd quits can report the ordinary shutdown procedure, but cannot reliably tell the trigger (greping for relevant journal entries works somewhat okay).
• When reasonably sure that a shutdown should not be attempted in the first place, I can use systemd-inhitibit instead, letting the other party figure out coordinating the shutdown with me.
• I know wall still works in modern times: shutdown time "wall message" does broadcast to all mesg y users. I could not find the place to enforce a default value.

After printing a document via cups, /var/log/cups/access_log contains the following log entry (and the printer did print):

"POST /printers/Brother HTTP/1.1" 200 70947 Print-Job successful-ok

However, the print job is not listed when querying via lpstat:

# lpstat -W all -u user
# lpstat -v
device for Brother: ipp://printer.test.:631/ipp/port

Why is lpstat not showing me the successfully executed print job?

I was wondering when nftables will become Canonical-supported in Ubuntu LTS, or how much longer the iptables tool chain is going to remain Canonical-supported, assuming such change happens in some future release.

What materials containing official deprecation timeline should I check (or re-check in the future) to figure out if such timelines are published already?

What I figured out so far:

• Searching in the package Index immediately reveals the universe tag in all currently supported Ubuntu releases, meaning inclusion in the main repositories has not yet begun
• sometimes packages are dropped from beta shortly before release, meaning any plans for packages in future releases is tentative before the actual release dates

What I tried unsuccessfully:

• retrieved changelogs of either package, nothing obvious in there
• did not find mailing list posts that announces specific plans
• not not find Network configuration sections in previous release notes that mention either
• USNs only mention issues (typically issues fixed) in already released packages
• subscribe to bugs on launchpad, those are rarely updated when issues are addressed

Every time I should be getting an error because a domain does not exist (e.g. could not resolve host), I instead get an error about connecting to a loopback address:

$ curl -4 -v https://nonexist.invalid
Trying 127.0.0.1...

The problem only starts occuring about 2 seconds after establishing a wireless connection. For a short time, all works as expected.

I am using systemd-resolved and dns appears to be working:

$ readlink /etc/resolv.conf
../run/systemd/resolve/stub-resolve.conf
$ dig +short A example.com
192.0.2.1
$ dig +short A nonexist.invalid
$ systemd-resolve -t A nonexist.invalid
nonexist.invalid: resolve call failed: No appropriate name servers or networks for name found

If name resolution looks okay, why would programs still appear to be resolving names to 127.0.0.1?

I would like to run the Ubuntu installer in qemu. I have used the kernel from the respective Ubuntu CD images and have verified my command line using the AMD64 architecture:

$ qemu-system-x86_64 --version
QEMU emulator version 2.5.0 ..
$ isoinfo -R -x "/install/vmlinuz" -i bionic-server-amd64.iso >linux
$ qemu-system-x86_64 -nodefaults -nographic -kernel linux \
   -serial stdio -append "console=ttyS0" \
   -machine pc -cpu qemu64 -m 1G
[    0.0000000] Linux version 4.15.0-44-generic ..

However, when I try the same thing for ARM64 architecture (not my host arch):

$ qemu-system-aarch64 --version
QEMU emulator version 2.5.0 ..
$ isoinfo -R -x "/install/vmlinuz" -i bionic-server-arm64.iso >linux
$ qemu-system-aarch64 -nodefaults -nographic -kernel linux \
   -serial stdio -append "console=ttyAMA0" \
   -machine virt -cpu cortex-a53 -m 1G

I get zero output at 100% cpu usage. How can i determine what went wrong?

Executing with -d unimp -D debug.log reveals:

read access to unsupported AArch64 system register op0:3 op1:0 crn:0 crm:7 op2:2

There are two /usr/lib/libreoffice/share/registry/*.xcd settings, each should suffice:

org.openoffice.Office.Misc/Security/Scripting/DisableMacroExecution=true
org.openoffice.Office.Misc/Security/Scripting/MacroSecurityLevel=3

After applying those, a macro from a loaded text document results in:

An attempt was made to execute a macro.
For security reasons, macro support is disabled.

However, macro support is not disabled. Adding a macro containing shell "xterm" to the current document and executing that still presents a terminal window.

Which options really disable the macro feature?

Is there a way to just not install the feature, instead of attempting to disable it?

Recently, my /etc/firefox/syspref.js stopped being applied. Unlike on Windows, where configuration errors results in

Failed to read the configuration file. Please contact your system administrator.

on my Ubuntu machines, firefox just silently ignores my settings. Launching with the -jsconsole switch reveals

** Preference parsing error (line 1) = non-matching string **

I did not make any changes to my /etc/firefox/syspref.js file. It did work in Firefox 58 and stopped working with the first Firefox 59 version. My file contains

// first line is ignored
lockPref("browser.startup.homepage", "https://example.org/");

What can i do to

1. temporarily mitigate the problem: Make firefox read my config again?
2. permanently solve the problem: Prevent firefox from starting with invalid configuration when it encounters syntax errors in my system-wide config?

A Xubuntu 16.04 fully patched machine with a freshly created user wont let me unlock after using light-locker to lock my screen (regardless if lock was activated manually or via timeout). The screen remains black (but powered) on correct password entry

Killing light-locker from tty1 will reveal the desktop then (and consequently prevents further locking).

Steps attempted:

• enabled/disabled lock in light-locker settings & in power settings (no change)
• used xscreensaver instead of light-locker (works)
• tested if issue is related to suspend or closing lid (it is not)
  • however, after suspend the black screen reveals the This session is locked: You will be redirected to the unlock dialog automatically in a few seconds message - without any redirection taking place
• purged+reinstalled lightdm, light-locker and xubuntu-default-settings
• using loginctl unlock-session has no effect
• systemctl status lightdm only reveals (harmless, expected) messages about kwallet pam module missing
• examined dpkg log for upgrades between "it worked" and "it doesn't work any more" (none suspicious) and booted previous kernel (issue persists)
• Compared behaviour between session-initiated light-locker and manually started one (no difference)
• added user to group nopasswdlogin group (black screen then occurs right after locking, not only after entering password)

What additional steps could prove useful in figuring out how to fix this?

Debugging log:

$ export LC_ALL=C; light-locker --debug & ( sleep 5; echo "## Locking now"; light-locker-command --lock; sleep 10; echo "### 10 seconds have passed - entering password now"; sleep 10; echo "### 10 more seconds have passwd - Killing"; killall light-locker; sleep 5; echo "### Killed now" )  
[1] 23463
[gs_debug_init] gs-debug.c:106 (00:08:32):   Debugging enabled
[main] light-locker.c:142 (00:08:32):    initializing light-locker 1.7.0
[main] light-locker.c:144 (00:08:32):    lock after screensaver 10
[main] light-locker.c:145 (00:08:32):    late locking 0
[main] light-locker.c:146 (00:08:32):    lock on suspend 1
[main] light-locker.c:147 (00:08:32):    lock on lid 0
[main] light-locker.c:148 (00:08:32):    idle hint 1
[query_session_id] gs-listener-dbus.c:2088 (00:08:32):   org.freedesktop.login1.NoSessionForPID raised:
 PID 23463 does not belong to any known session


[init_session_id] gs-listener-dbus.c:2180 (00:08:32):    Got session-id: (null)
[query_sd_session_id] gs-listener-dbus.c:2164 (00:08:32):    Couldn't determine our own sd session id: No such process
[init_session_id] gs-listener-dbus.c:2185 (00:08:32):    Got sd-session-id: (null)
[init_seat_path] gs-listener-dbus.c:2262 (00:08:32):     Got seat: /org/freedesktop/DisplayManager/Seat0
[gs_listener_delay_suspend] gs-listener-dbus.c:449 (00:08:32):   Delay suspend
[gs_listener_x11_acquire] gs-listener-x11.c:172 (00:08:32):  ScreenSaver Registered
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:32):    obj_path=/org/freedesktop/DBus interface=org.freedesktop.DBus method=NameAcquired destination=:1.316
## Locking now
[gs_grab_grab_root] gs-grab-x11.c:647 (00:08:37):    Grabbing the root window
[gs_grab_get_keyboard] gs-grab-x11.c:153 (00:08:37):     Grabbing keyboard widget=E3
[gs_grab_get_mouse] gs-grab-x11.c:213 (00:08:37):    Grabbing mouse widget=E3
[gs_manager_create_windows_for_screen] gs-manager.c:548 (00:08:37):  Creating 1 windows for screen 0
[gs_manager_create_window_for_monitor] gs-manager.c:324 (00:08:37):  Creating window for monitor 0 [0,0] (1600x900)
[update_geometry] gs-window-x11.c:197 (00:08:37):    got geometry for monitor 0: x=0 y=0 w=1600 h=900
[update_geometry] gs-window-x11.c:210 (00:08:37):    using geometry for monitor 0: x=0 y=0 w=1600 h=900
[update_geometry] gs-window-x11.c:197 (00:08:37):    got geometry for monitor 0: x=0 y=0 w=1600 h=900
[update_geometry] gs-window-x11.c:210 (00:08:37):    using geometry for monitor 0: x=0 y=0 w=1600 h=900
[gs_window_move_resize_window] gs-window-x11.c:243 (00:08:37):   Move and/or resize window on monitor 0: x=0 y=0 w=1600 h=900
[update_geometry] gs-window-x11.c:197 (00:08:37):    got geometry for monitor 0: x=0 y=0 w=1600 h=900
[update_geometry] gs-window-x11.c:210 (00:08:37):    using geometry for monitor 0: x=0 y=0 w=1600 h=900
[gs_window_move_resize_window] gs-window-x11.c:243 (00:08:37):   Move and/or resize window on monitor 0: x=0 y=0 w=1600 h=900
[update_geometry] gs-window-x11.c:197 (00:08:37):    got geometry for monitor 0: x=0 y=0 w=1600 h=900
[update_geometry] gs-window-x11.c:210 (00:08:37):    using geometry for monitor 0: x=0 y=0 w=1600 h=900
[gs_window_move_resize_window] gs-window-x11.c:243 (00:08:37):   Move and/or resize window on monitor 0: x=0 y=0 w=1600 h=900
[gs_manager_timed_switch] gs-manager.c:445 (00:08:37):   Start switch to greeter timer
[gs_window_xevent] gs-window-x11.c:369 (00:08:37):   not raising our windows
[window_map_event_cb] gs-manager.c:233 (00:08:37):   Handling window map_event event
[gs_listener_resume_suspend] gs-listener-dbus.c:513 (00:08:37):  Resume suspend: fd=14
[manager_maybe_grab_window] gs-manager.c:204 (00:08:37):     Moving grab to 0x5595f8d5a290
[gs_grab_move_keyboard] gs-grab-x11.c:450 (00:08:37):    Moving keyboard grab from E3 to 3A0000C
[gs_grab_move_keyboard] gs-grab-x11.c:457 (00:08:37):    *** doing X server grab
[gs_grab_release_keyboard] gs-grab-x11.c:279 (00:08:37):     Ungrabbing keyboard
[gs_grab_get_keyboard] gs-grab-x11.c:153 (00:08:37):     Grabbing keyboard widget=3A0000C
[gs_grab_move_keyboard] gs-grab-x11.c:479 (00:08:37):    *** releasing X server grab
[gs_grab_move_mouse] gs-grab-x11.c:395 (00:08:37):   Moving pointer grab from E3 to 3A0000C
[gs_grab_move_mouse] gs-grab-x11.c:402 (00:08:37):   *** doing X server grab
[gs_grab_release_mouse] gs-grab-x11.c:320 (00:08:37):    Ungrabbing pointer
[gs_grab_get_mouse] gs-grab-x11.c:213 (00:08:37):    Grabbing mouse widget=3A0000C
[gs_grab_move_mouse] gs-grab-x11.c:425 (00:08:37):   *** releasing X server grab
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:37):    obj_path=/org/freedesktop/login1 interface=org.freedesktop.DBus.Properties method=PropertiesChanged destination=(null)
[update_geometry] gs-window-x11.c:197 (00:08:37):    got geometry for monitor 0: x=0 y=0 w=1600 h=900
[update_geometry] gs-window-x11.c:210 (00:08:37):    using geometry for monitor 0: x=0 y=0 w=1600 h=900
[gs_window_move_resize_window] gs-window-x11.c:243 (00:08:37):   Move and/or resize window on monitor 0: x=0 y=0 w=1600 h=900
[update_geometry] gs-window-x11.c:197 (00:08:37):    got geometry for monitor 0: x=0 y=0 w=1600 h=900
[update_geometry] gs-window-x11.c:210 (00:08:37):    using geometry for monitor 0: x=0 y=0 w=1600 h=900
[gs_window_move_resize_window] gs-window-x11.c:243 (00:08:37):   Move and/or resize window on monitor 0: x=0 y=0 w=1600 h=900
[gs_listener_send_lock_session] gs-listener-dbus.c:180 (00:08:38):   Send lock session
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:38):    obj_path=(null) interface=(null) method=(null) destination=:1.316
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:39):    obj_path=/org/freedesktop/login1/session/c5 interface=org.freedesktop.DBus.Properties method=PropertiesChanged destination=(null)
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:39):    obj_path=/org/freedesktop/login1/session/c12 interface=org.freedesktop.DBus.Properties method=PropertiesChanged destination=(null)
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:39):    obj_path=/org/freedesktop/login1/seat/seat0 interface=org.freedesktop.DBus.Properties method=PropertiesChanged destination=(null)
process 23463: arguments to dbus_message_new_method_call() were incorrect, assertion "path != NULL" failed in file ../../dbus/dbus-message.c line 1340.
This is normally a bug in some application using the D-Bus library.
[query_session_active] gs-listener-dbus.c:1124 (00:08:39):   Couldn't allocate the dbus message
[listener_dbus_handle_system_message] gs-listener-dbus.c:1361 (00:08:39):    systemd notified ActiveSession 0
[listener_session_switched_cb] gs-monitor.c:298 (00:08:39):  Session switched: 0
[gs_manager_stop_switch] gs-manager.c:456 (00:08:39):    Stop switch to greeter timer
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:39):    obj_path=/org/freedesktop/login1/seat/seat0 interface=org.freedesktop.DBus.Properties method=PropertiesChanged destination=(null)
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:39):    obj_path=/org/freedesktop/login1/session/c12 interface=org.freedesktop.DBus.Properties method=PropertiesChanged destination=(null)
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:39):    obj_path=/org/freedesktop/login1/user/_108 interface=org.freedesktop.DBus.Properties method=PropertiesChanged destination=(null)
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:39):    obj_path=/org/freedesktop/login1/seat/seat0 interface=org.freedesktop.DBus.Properties method=PropertiesChanged destination=(null)
process 23463: arguments to dbus_message_new_method_call() were incorrect, assertion "path != NULL" failed in file ../../dbus/dbus-message.c line 1340.
This is normally a bug in some application using the D-Bus library.
[query_session_active] gs-listener-dbus.c:1124 (00:08:39):   Couldn't allocate the dbus message
[listener_dbus_handle_system_message] gs-listener-dbus.c:1361 (00:08:39):    systemd notified ActiveSession 0
[listener_session_switched_cb] gs-monitor.c:298 (00:08:39):  Session switched: 0
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:39):    obj_path=/org/freedesktop/login1/session/c5 interface=org.freedesktop.login1.Session method=Lock destination=(null)
### 10 seconds have passed - entering password now
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:51):    obj_path=/org/freedesktop/login1/session/c5 interface=org.freedesktop.login1.Session method=Unlock destination=(null)
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:51):    obj_path=/org/freedesktop/login1/session/c13 interface=org.freedesktop.DBus.Properties method=PropertiesChanged destination=(null)
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:51):    obj_path=/org/freedesktop/login1/session/c5 interface=org.freedesktop.DBus.Properties method=PropertiesChanged destination=(null)
[listener_dbus_handle_system_message] gs-listener-dbus.c:1330 (00:08:51):    obj_path=/org/freedesktop/login1/seat/seat0 interface=org.freedesktop.DBus.Properties method=PropertiesChanged destination=(null)
process 23463: arguments to dbus_message_new_method_call() were incorrect, assertion "path != NULL" failed in file ../../dbus/dbus-message.c line 1340.
This is normally a bug in some application using the D-Bus library.
[query_session_active] gs-listener-dbus.c:1124 (00:08:51):   Couldn't allocate the dbus message
[listener_dbus_handle_system_message] gs-listener-dbus.c:1361 (00:08:51):    systemd notified ActiveSession 0
[listener_session_switched_cb] gs-monitor.c:298 (00:08:51):  Session switched: 0
[xroot_filter] gs-listener-x11.c:124 (00:08:52):     ScreenSaver stopped
### 10 more seconds have passwd - Killing
### Killed now

Diffing this to a known-good system yields:

$ comm -3 <(grep -iv grab good | sed 's/[0-9:]\+/[NN]/g;s/[ \t]\+/ /g' | sort) <(grep -iv grab bad | sed 's/[0-9:]\+/[NN]/g;s/[ \t]\+/ /g' | sort) | head -n2
[init_session_id] gs-listener-dbus.c[NN] ([NN])[NN] Got session-id[NN] (null)
[init_session_id] gs-listener-dbus.c[NN] ([NN])[NN] Got session-id[NN] /org/freedesktop/login[NN]/session/c[NN]

And indeed, something appears to be very awkward about session setup:

$ loginctl session-status
Could not get properties: No such process

I use my Ubuntu 14.04 and 16.04 notebooks for development purposes and regularily run various servers (e.g. web servers) on a network address not otherwise accessible from the internet.

How do I avoid still exposing such servers to the world via my web browsers, in case someone rebinds his domain name to a private IP?

The attack is further described in https://en.wikipedia.org/wiki/DNS_rebinding

When attempting to resize and old ext4 Partition that was created without the 64bit flag, resize2fs 1.42 will fail if the new size is or exceeds 16TiB.

$ resize2fs -p /dev/mapper/target-device
resize2fs: New size too large to be expressed in 32 bits

I do not want to copy the files to an external medium. I do not want to risk data loss either. How can i resize the volume safely?

I am trying to debug an unsecessful/hung-up system start (upstart) on 14.04.2 LTS. root is an ext4 filesystem in a luks container. filesystems are in clean state.

The boot process stops after upstart-socket-bridge, (not necessarily after that specific service, e.g. when cups-daemon was installed, it stoped after that). init -v isnt very helpful either. The only log entry that isnt merely logging the start/stop of various services is one about udev right before init.

Begin: Running /scripts/init-bottom ... done.
udev exit failed --rc=2

(Edit) Remounting the root rw initially appeared to be always leading to a clean boot, but fact is, its kinda unpredictable and i had failed and successful boots either way. wut?

Observation: Everything appears to be fine, the system simply doesnt remounts the root writable or continues the boot.

Q: How do i figure which service is at fault for getting the boot process stuck?

Update: Spawning a second shell via getty one can run initctl list after it hangs up, these are the running jobs

mountnfs-bootclean.sh start/running
udev start/running, process 438
upstart-udev-bridge start/running, process 432
plymouth start/running, process 122
resolvconf start/running
ssh start/running, process 767 <-- this one was manually started
mountall start/running, process 337
mountkernfs.sh start/running
mountnfs.sh start/running
bootmisc.sh start/running
upstart-socket-bridge start/running, process 745**
cryptdisks start/running
mountdevsubfs.sh start/running
mtab.sh start/running
network-interface (lo) start/running
network-interface (eth0) start/running
plymouth-ready (startup) start/running, process 315
plymouth-upstart-bridge start/running, process 316
mountall-bootclean.sh start/running
network-interface-security (network-interface/eth0) start/running
network-interface-security (network-interface/lo) start/running

Update 2:

• Reinstaling upstart and all its dependant packets (is a pain and) has no effect.
• Using the second console, i can just use init 5 to get the stuck system to continue boot normally.
• the system now got stuck even if i manually remounted the root rw (or used the rw kernel parameter) - my initial observation that forcing the root writable works around the issue is incorrect

Workaround:

It appears to be ureadaheads fault. Purging it resulted in 5 clean boots withouth any issue. I'll just leave the question (and the 100 extra rep) open for anyone interested or knowing an answer for the original question: How, if not by random trial, i could have figured this out.