我什至不知道从哪里开始诊断这个。通常，当一个命令完成时，提示符会为下一个命令打印自己。然而，这并没有发生。很难用语言来解释，我就举个例子：
User@Machine:~$ cp /mnt/mountname/directory/textfile.txt .
等待几秒钟后（对于小文件的这个操作来说太长了），我按下Enter，然后看到：
User@Machine:~$ cp /mnt/mountname/directory/textfile.txt .
User@Machine:~$
User@Machine:~$
很明显操作完成了，但是提示没有显示......直到我按下回车，然后两个提示立即显示。
这基本上只是整体上的滞后问题。关于导致它的原因没有真正的可预测性。我尝试升级到 12.04.3（3.8 内核，lts-raring），但没有帮助。
更新：刚才我fgrep在一个大文本文件上做了一个，它正确返回。但是之后我ls立即打字，直到我再次按下 Enter 键才打印任何内容。这种行为似乎比其他任何事情都不一致。
更新 2：在某些时候，我认为一些软件包被删除了。我与dpkg --get-selected12.04 清单进行了比较；这是未安装的软件包。它们中的任何一个丢失会导致问题吗？
activity-log-manager-common
activity-log-manager-control-center
appmenu-gtk3
appmenu-qt
apt-clone
archdetect-deb
brasero-cdrkit
colord
cryptsetup
cryptsetup-bin
dmraid
duplicity
ecryptfs-utils
enchant
firefox-locale-es
firefox-locale-zh-hans
folks-common
fonts-nanum
geoclue
geoclue-ubuntu-geoip
gir1.2-dbusmenu-gtk-0.4
gir1.2-ubuntuoneui-3.0
gnome-online-accounts
gwibber-service-facebook
gwibber-service-identica
gwibber-service-twitter
hplip
ibus-pinyin
ibus-pinyin-db-android
indicator-appmenu
indicator-datetime
indicator-power
indicator-printers
indicator-status-provider-mc5
keyutils
kpartx
kpartx-boot
krb5-locales
landscape-client-ui-install
language-pack-es
language-pack-es-base
language-pack-gnome-es-base
language-pack-gnome-zh-hans
language-pack-gnome-zh-hans-base
language-pack-zh-hans
language-pack-zh-hans-base
libdebconfclient0
libdebian-installer4
libfile-mimeinfo-perl
libfreerdp-plugins-standard
libfreerdp1
libgphoto2-l10n
libmtp-runtime
liboverlay-scrollbar3-0.2-0
libpam-cap
libqt4-sql-sqlite
libreoffice-style-tango
libsane-hpaio
libsnmp15
overlay-scrollbar
printer-driver-c2esp
printer-driver-gutenprint
printer-driver-hpcups
printer-driver-hpijs
printer-driver-postscript-hp
printer-driver-ptouch
printer-driver-sag-gdi
python-dateutil
python-libproxy
python-packagekit
python-reportlab-accel
python-ubuntuone-control-panel
python-zeitgeist
qt-at-spi
remmina-common
remmina-plugin-rdp
remmina-plugin-vnc
rhythmbox-mozilla
rhythmbox-plugin-magnatune
rhythmbox-plugin-zeitgeist
sessioninstaller
sni-qt
telepathy-indicator
thunderbird
thunderbird-globalmenu
thunderbird-gnome-support
ubiquity-frontend-gtk
ubiquity-slideshow-ubuntu
ubiquity-ubuntu-artwork
ubuntuone-control-panel
ubuntuone-couch
ubuntuone-installer
unity-lens-applications
unity-lens-files
unity-lens-music
unity-lens-video
unity-scope-musicstores
unity-scope-video-remote
usb-modeswitch
usb-modeswitch-data
user-setup
xfsprogs
zeitgeist
zeitgeist-core
zeitgeist-datahub
更新 3：回复评论，输出$ sudo dpkg -l | grep -e "iU" -e "rc"：
ii apt-xapian-index 0.44ubuntu5.1 maintenance and search tools for a Xapian index of Debian packages
rc bugzilla3 3.2.5.1-2 web-based bug tracking system
rc capplets-data 1:2.30.1-0ubuntu2 configuration applets for GNOME - data files
ii cpio 2.11-7ubuntu3 GNU cpio -- a program to manage archives of files
rc cups-driver-gutenprint 5.2.5-0ubuntu1.1 printer drivers for CUPS
rc esound-clients 0.2.41-6ubuntu1 Enlightened Sound Daemon - clients
ii evolution-common 3.2.3-0ubuntu6 architecture independent files for Evolution
ii evolution-data-server-common 3.2.3-0ubuntu7.1 architecture independent files for Evolution Data Server
ii file-roller 3.4.1-0ubuntu1 archive manager for GNOME
rc gdm-guest-session 0.15ubuntu0.1 gdm extension for guest session
ii gir1.2-gtksource-3.0 3.4.2-0ubuntu1 gir files for the GTK+ syntax highlighting widget
rc gnome-games-common 1:2.30.0-0ubuntu6 Common files for GNOME Games
rc gnome-mahjongg 1:2.30.0-0ubuntu6 Mahjongg tile solitaire game
ii gnome-orca 3.4.2-0ubuntu0.1 Scriptable screen reader
ii gnome-search-tool 3.4.0-1 GNOME tool to search files
ii gnome-system-monitor 3.4.1-0ubuntu1 Process viewer and system resource monitor for GNOME
ii gs-cjk-resource 1.20100103-3 Resource files for gs-cjk, ghostscript CJK-TrueType extension
ii gstreamer0.10-gconf 0.10.31-1ubuntu1.2 GStreamer plugin for getting the sink/source information from GConf
ii gwibber 3.4.2-0ubuntu2.3 Open source social networking client for GNOME
ii gwibber-service 3.4.2-0ubuntu2.3 Open source social networking client for GNOME
rc hplip 3.10.2-2ubuntu2.2 HP Linux Printing and Imaging System (HPLIP)
rc irb1.8 1.8.7.249-2ubuntu0.2 Interactive Ruby (for Ruby 1.8)
ii libarchive1 2.8.0-2ubuntu0.1 Single library to read/write tar, cpio, pax, zip, iso9660, etc.
ii libarchive12 3.0.3-6ubuntu1 Multi-format archive and compression library (shared library)
ii libaudiofile0 0.2.6-8ubuntu1 Open-source version of SGI's audiofile library
ii libaudiofile1 0.3.3-2 Open-source version of SGI's audiofile library
rc libbrasero-media0 2.30.2-0ubuntu1.1 CD/DVD burning library for GNOME - runtime
ii libclass-isa-perl 0.36-3 report the search path for a class's ISA tree
rc libdrm-nouveau1 2.4.18-1ubuntu3 Userspace interface to nouveau-specific kernel DRM services -- runtime
rc libept0 0.5.30 High-level library for managing Debian package information
ii libffi6 3.0.11~rc1-5 Foreign Function Interface library runtime
ii libgd2-xpm 2.0.36~rc1~dfsg-6ubuntu2 GD Graphics Library version 2
rc libgl1-mesa-dri 9.0-0ubuntu1 free implementation of the OpenGL API -- DRI modules
rc libgl1-mesa-glx 9.0-0ubuntu1 free implementation of the OpenGL API -- GLX runtime
rc libglapi-mesa 9.0-0ubuntu1 free implementation of the GL API -- shared library
rc libgraphviz4 2.20.2-8ubuntu3 rich set of graph drawing tools
rc libgstfarsight0.10-0 0.0.17-2ubuntu2 Audio/Video communications framework: core library
ii libgtksourceview-3.0-0 3.4.2-0ubuntu1 shared libraries for the GTK+ syntax highlighting widget
ii libgtksourceview-3.0-common 3.4.2-0ubuntu1 common files for the GTK+ syntax highlighting widget
ii libgtksourceview2.0-0 2.10.5-0ubuntu3 shared libraries for the GTK+ syntax highlighting widget
ii libgtksourceview2.0-common 2.10.5-0ubuntu3 common files for the GTK+ syntax highlighting widget
rc libgvfscommon0 1.6.1-0ubuntu1build1 userspace virtual filesystem - library
rc libhpmud0 3.10.2-2ubuntu2.2 HP Multi-Point Transport Driver (hpmud) run-time libraries
ii libkpathsea5 2009-11ubuntu2 TeX Live: path search library for TeX (runtime part)
ii liblircclient0 0.9.0-0ubuntu1 infra-red remote control support - client library
rc libllvm3.1 3.1-2ubuntu1~12.04.1 Low-Level Virtual Machine (LLVM), runtime library
rc libmtp8 1.0.2-1ubuntu1 Media Transfer Protocol (MTP) library
rc libnm-glib2 0.8-0ubuntu3.3 network management framework (GLib shared library)
rc libntfs-3g75 1:2010.3.6-1ubuntu1 ntfs-3g filesystem in userspace (FUSE) library
ii libnuma1 2.0.8~rc3-1 Libraries for controlling NUMA policy
rc libodbcinstq1c2 2.2.11-21 Qt-based ODBC configuration library
ii liborc-0.4-0 1:0.4.16-1ubuntu2 Library of Optimized Inner Loops Runtime Compiler
rc libpanel-applet2-0 1:2.30.2-0ubuntu0.2 library for GNOME Panel applets
rc libpolkit-gtk-1-0 0.96-2ubuntu2 PolicyKit GTK+ API
rc libpulse-browse0 1:0.9.22~0.9.21+stable-queue-32-g8478-0ubuntu14 PulseAudio client libraries (zeroconf support)
ii librdf0 1.0.14-1 Redland Resource Description Framework (RDF) library
ii libreoffice-common 1:3.5.7-0ubuntu4 office productivity suite -- arch-independent files
ii libreoffice-core 1:3.5.7-0ubuntu4 office productivity suite -- arch-dependent files
rc librpm0 4.7.2-1lbuild1 RPM shared library
rc librpmbuild0 4.7.2-1lbuild1 RPM build shared library
rc librpmio0 4.7.2-1lbuild1 RPM IO shared library
rc libsdl1.2debian-pulseaudio 1.2.14-4ubuntu1.1 Simple DirectMedia Layer (with X11 and PulseAudio options)
rc libsnmp15 5.4.2.1~dfsg0ubuntu1-0ubuntu2.2 SNMP (Simple Network Management Protocol) library
ii libspeex1 1.2~rc1-3ubuntu2 The Speex codec runtime library
ii libspeexdsp1 1.2~rc1-3ubuntu2 The Speex extended runtime library
ii libtalloc2 2.0.7-3 hierarchical pool based memory allocator
rc libtelepathy-farsight0 0.0.13-1 Glue library between telepathy and farsight2
rc libturbojpeg 1.1.90+svn733-0ubuntu4.1 IJG JPEG compliant runtime library.
ii libusb-1.0-0 2:1.0.9~rc3-2ubuntu1 userspace USB programming library
ii libxapian15 1.0.18-1 Search engine library
ii libxapian22 1.2.8-1 Search engine library
rc libxatracker1 9.0-0ubuntu1 X acceleration library -- runtime
rc libxen3 3.3.0-1ubuntu11 library interface for Xen, a Virtual Machine Monitor
ii libxres1 2:1.0.5-1ubuntu0.1 X11 Resource extension library
ii libxvidcore4 2:1.3.2-6 Open source MPEG-4 video codec (library)
ii multiarch-support 2.15-0ubuntu10.5 Transitional package to ensure multiarch compatibility
rc mysql-server-5.1 5.1.66-0ubuntu0.10.04.1 MySQL database server binaries
rc nvidia-304 304.88-0ubuntu0.0.3 NVIDIA binary Xorg driver, kernel module and VDPAU library
rc nvidia-304-updates 304.88-0ubuntu0.0.3 NVIDIA binary Xorg driver, kernel module and VDPAU library
rc nvidia-experimental-304 304.48-0ubuntu0.1 Experimental NVIDIA binary Xorg driver, kernel module and VDPAU library
rc odbcinst1debian1 2.2.11-21 Support library for accessing odbc ini files
ii openjdk-7-jre-lib 7u25-2.3.10-1ubuntu0.12.04.2 OpenJDK Java runtime (architecture independent libraries)
ii openoffice.org-common 1:3.3.0-7ubuntu7 office productivity suite -- arch-independent files
rc openoffice.org-core 1:3.2.0-7ubuntu4.4 office productivity suite -- arch-dependent files
ii pax 1:20120216-1 Portable Archive Interchange (cpio, pax, tar)
ii php5-common 5.3.10-1ubuntu3.8 Common files for packages built from the php5 source
ii python-gtksourceview2 2.10.1-2build1 Python bindings for the GtkSourceView widget
ii python-pkg-resources 0.6.24-1ubuntu1 Package Discovery and Resource Access using pkg_resources
rc python-ubuntuone 0.3.1-0ubuntu1 Ubuntu One widget library
ii python-xapian 1.2.8-1 Xapian search engine interface for Python
rc rake 0.9.2.2-2 ruby make-like utility
rc redmine 1.3.2+dfsg1-1ubuntu1 flexible project management web application
rc rhythmbox-ubuntuone-music-store 0.0.9-0ubuntu1 Ubuntu One Music Store Rhythmbox plugin
ii rpm2cpio 4.9.1.1-1ubuntu0.2 tool to convert RPM package to CPIO archive
ii smartdimmer 0.8b4+cvs20100914-1ubuntu2 Change LCD brightness on Geforce cards
rc speech-dispatcher 0.7.1-6ubuntu3 Common interface to speech synthesizers
ii sysv-rc 2.88dsf-13.10ubuntu11.1 System-V-like runlevel change mechanism
ii tar 1.26-4ubuntu1 GNU version of the tar archiving utility
ii time 1.7-23.1 The GNU time program for measuring cpu resource usage
rc tsclient 0.150-3ubuntu1 front-end for viewing of remote desktops in GNOME
ii ubuntu-extras-keyring 2010.09.27 GnuPG keys of the Ubuntu extras archive
ii ubuntu-keyring 2011.11.21.1 GnuPG keys of the Ubuntu archive
ii unzip 6.0-4ubuntu2 De-archiver for .zip files
rc virtualgl-libs 2.3.2-1~preciseppa2 Library files for virtualgl
ii xdg-utils 1.1.0~rc1-2ubuntu6 desktop integration utilities from freedesktop.org
ii zip 3.0-4 Archiver for .zip files
我的猜测是，这是 gnome 终端（我假设这是您正在使用的终端）、图形/桌面子系统或它们之间的某些交互中的错误。是实际的键盘输入触发了缺失行的出现，还是向下滚动（例如使用鼠标滚轮）来触发缺失行？我以前在 gt 中见过类似的错误，我认为最后一个错误与切换或创建选项卡有关。
之前报告的类似错误的示例：
https://bugs.launchpad.net/ubuntu/+source/gnome-terminal/+bug/881014 https://bugzilla.redhat.com/show_bug.cgi?id=695412
我建议尝试使用不同的终端程序（例如 xterm），也许使用不同的窗口管理器或桌面环境（例如在 unity 和 unity-2d 之间交换）或图形驱动程序（例如在 nouveau 和 nvidia 专有驱动程序之间交换。）遗憾的是，实际上追查 gnome-terminal 中的错误并修复它可能不太可能。
我非常怀疑丢失的包裹是原因。