Ubuntu Blog: Usefull Linux Terminal Commands

aspell (command line spell checking)

aspell -c
 sample.tex

aspell
 -dont-backup -c sample.tex

aspell dump
 personal

sudo updatedb

locate .aspell*

cat
 ~/.aspell.en.pws

aspell dump config

apt/dpkg (package management, software installation)

sudo apt-get
 install package_name

sudo apt-get
 remove package_name

sudo
 apt-add-repository ppa:sample_ppa/sample

sudo apt-get update

apt-cache search
 search_term

dpkg -l

dpkg -L
 package_name

cp/mv/rm (copy, move, delete files)

cp /example/file1
 /example/file2

cp -a
 /example/dir1 /example/dir2

mv /example/file1
 /example/file2

rm /example/file1

rm -rf
 /example/dir

dd (clone a hard drive, backup drive to file)

sudo fdisk -l

(note: drive /dev/sdb must have size greater than or equal to /dev/sda)

sudo dd
 if=/dev/sda of=/dev/sdb

(note: output file location should not be on any partition of /dev/sda)

sudo dd
 if=/dev/sda of=/home/sda_as_backup_file

ps au | grep dd

sudo watch -n 10
 "kill -USR1 processid"

sudo blkid

tune2fs -U random
 /dev/sda1

df/du/find (drive usage)

df -h

sudo du -hsx /* |
 sort -n

find -size +100M
 -ls

ffmpeg (video transcoding, desktop recording, etc.)

ffmpeg -f x11grab
 -y -r 24 -s 1920x1080 -i :0+0,0 -vcodec mpeg4 -sameq sample_out.mp4

ffmpeg -f x11grab
 -y -r 24 -s 400x400 -i :1+200,200 -vcodec mpeg4 -sameq
 sample_out.mp4

ffmpeg -f alsa -ac
 2 -i hw:0 -i /dev/video0 -acodec ac3 -ab 128k -vcodec mpeg4 -sameq
 -r 24 sample_out.mp4

ffmpeg -i
 sample.mp4 -sameq -s hd720 sample_720.mp4

ffmpeg -i
 sample.mp4 -vcodec copy -acodec aac -sameq sample_out.mp4

ffmpeg -i
 sample.mp4 -vf "setpts=0.05*PTS" -r 25 -s hd720 -sameq
 sample_out.mp4

ffmpeg -i
 sample.mp4 -vf "transpose=1" -sameq sample_out.mp4

ffmpeg -i
 sample.mp4 -vf "transpose=2" -sameq sample_out.mp4

ffmpeg -i
 sample.mp4 -aspect 4:3 -vf "movie=overlay.png [logo];
 [in][logo] overlay=0:0:1" -sameq sample_out.mp4

Images

video

ffmpeg -r 1 -i
 dgplogo%01d_1080.png -sameq sample_out.mp4

ffmpeg -i
 "concat:sample1.avi|sample2.avi" -vcodec copy -acodec copy
 sample_out.mp4

gcc (creating software programs)

gcc -c sample.c -o
 sample.o

ar crs libsample.a
 sample.o

gcc -shared -o
 libsample.so sample.o

gcc -static test.c
 -L. -lsample -o test_static

gcc test.c -L.
 -lsample -o test_shared

(General) Append path to /etc/ld.so.conf

(Ubuntu) Append
 path to /etc/ld.so.conf.d/.conf

sudo ldconfig

#!/bin/bash

LD_LIBRARY_PATH=/directory/for/libs/:$LD_LIBRARY_PATH

echo 'looking for shared libraries here first'
 $LD_LIBRARY_PATH

/path/to/executable

ldd
 /path/to/executable

gcc -S -c sample.c

git (revision control system)

git config --global user.name "My Name"

git config --global user.email
 "example@email.ca"

git config
 merge.tool kdiff3

git clone
 https://github.com/Example/repo.git

git remote add upstream
 https://github.com/Example/repo.git

git remote -v

git log upstream

git show

git fetch

git branch -r

git branch

git branch -D
 branch_name

git add
 /path/to/files

git commit -a -m'made some changes'

git push origin master

git pull upstream
 master

git stash

git merge
 origin/some_branch

git status

git mergetool

git reset --hard
 commit_hash_value

git branch
 new_branch

git checkout
 new_branch

grep (search files for strings)

grep search_string
 filename

grep -n
 search_string filename

grep -l
 search_string filenames*

locate (search for files/directories)

locate
 'search_term1 search_term2'

locate -i
 search_term

sudo updatedb

whereis
 program_name

which program_name

man (software documentation)

man program_name

man -k keyword

apropos keyword

mount (enabling access to drives/filesystems)

mount

sudo mkdir /media/drivedir

sudo mount
 /dev/sda1 /media/drivedir

sudo umount
 /media/drivedir

rsync (backups)

rsync -av
 source_path dest_path

rsync -av
 --delete-excluded --ignore-errors --exclude=*.gvfs*
 --exclude='.local' source_path dest_path

#!/bin/bash

echo "Backing up..."

# may want to mount drive for source/dest paths
 first here

rsync -av
 source_path dest_path

chmod 744
 ./backup.sh

chown james:james
 /media/james/Drive -R

ssh (log into another machine)

ssh
 username@server_address

ssh-keygen -t rsa

ssh-add -l

ssh-add
 /path/to/private_key

ssh-keygen -lf
 /path/to/key

tar/gzip (archive, compress)

tar -czvf
 file.tar.gz /path/to/compress/

tar -xvf
 file.tar.gz

gzip input_file

gunzip
 input_file.gz

On getting nvidia_experimental_310 to work:

I had issues getting the nvidia_experimental_310 package working. It turned out there was a "nvidia_experimental_310" entry in a file "/etc/modprobe.d/blacklist-local.conf" causing the trouble. How and why that got there I may never know. Commands I tried to track down this problem and my path to a solution:
Show loaded modules (with 'nvidia' in name):

lsmod | grep nvidia

Not loaded. Show errors in X.org log:

cat
/var/log/Xorg.0.log | grep '(EE)'

Error found, suggests checking kernel log:
[ 10.865] (EE) NVIDIA: Failed to load the NVIDIA kernel module. Please check your
[ 10.865] (EE) NVIDIA: system's kernel log for additional error messages.
[ 10.865] (EE) Failed to load module "nvidia" (module-specific error, 0)
Show kernel log (and view in 'less'):

cat
/var/log/kern.log | less

Last entry shows it trying to load nvidia module? Not very helpful unfortunately.
Show all nvidia kernel objects:

locate *.ko | grep
nvidia

...
/lib/modules/3.5.0-21-generic/updates/dkms/nvidia_experimental_310.ko
Existence of the kernel object for the current version of the kernel I'm running (uname -r) is encouraging as it means when installing the nvidia_experimental_310 package it compiled OK. Let's try to link it into the kernel again ourselves.
Load a module (in this case, 'nvidia_experimental_310'):

sudo modprobe
nvidia_experimental_310

modprobe: WARNING: Not loading blacklisted module nvidia_experimental_310
Blacklisted? Huh?
Search all blacklisted modules (whose name contains 'nvidia'):

cat
/etc/modprobe.d/blacklist* | grep nvidia

blacklist nvidiafb
blacklist nvidia_experimental_310
Aha! After removing blacklist-local.conf which contained the above entry, I tried again.
Load a module, then restart display manager:

sudo modprobe nvidia_experimental_310

sudo service
restart lightdm

Working well!

copy/pasting into the terminal:

"Control-Shift-V" pastes text directly into the terminal, avoiding the need to right click and choose "Paste" each time.

filesystem mounting options for a solid state drive:

You can edit "fstab" (the file system table) by doing the following:

gksudo gedit
/etc/fstab

To identify which is the SSD:

blkid

Listing all partition information can be helpful to identify the drive:

sudo fdisk -l

Under "options" in the fstab, for the SSD, adding discard adds TRIM support, adding noatime, nodiratime disables extra writes to keep track of when files and directories were last accessed. For instance if the SSD line in fstab is:

UUID=03f7d0a1-2fcb-4878-afef-8487799df4a4
/ ext4 errors=remount-ro 0 1

Change it to the following, using commas to separate each option:

UUID=03f7d0a1-2fcb-4878-afef-8487799df4a4
/ ext4 discard,noatime,nodiratime,errors=remount-ro 0 1

Do not forget to save and restart.

using udisks and gnome-session-properties to automount partitions on login:

The easiest way to set up automatic mounting is using the gnome-disks tool, and choosing "Edit mount options...". The next easiest way is by running gnome-session-properties and add the following command:

/usr/bin/udisks
--mount /dev/sdb1

where "/dev/sdb1" the partition you wish to mount. Using a UUID is preferred in case drives get switched around, to view partition UUIDs use:

blkid

Given the UUID of the partition, change the udisks command parameters to:

/usr/bin/udisks
--mount /dev/disk/by-uuid/1234567890ABCD

Or, one can edit the filesystem table file (/etc/fstab).

changing file ownership on a USB drive not formatted to FAT32:

The drive will not allow you to write to it since you are not the owner of files on that filesystem (the root account is). Chances are, while FAT* does not support the concept of user ownership, the existing filesystem does (e.g. ext4), causing the problem. Use the "chown" command to change the ownership to your account. With the drive mounted, do:

sudo chown james
/media/james/kingston32gb

This changes the files mounted to /media/james/kingston32gb to be owned by user james. You will then be able to both read and write files to the device.

getting multi-monitor settings with nvidia-settings to stick after reboot:

I had an issue with three display devices having their positions reset every reboot (two standard monitors, plus an Oculus Rift). The Oculus Rift would always be reset to be positioned between the two monitors. Using nvidia-settings and saving to /etc/X11/xorg.conf never seemed to work. Bring up a terminal and run:

gksudo
nvidia-settings

Set the desired display configuration. Then, save xorg.conf configuration settings to:

/usr/share/X11/xorg.conf.d/xorg.conf

You may notice when browsing the directory /usr/share/X11/xorg.conf.d/ that a file xorg.conf.backup was instead saved. You can copy or rename this file using gksudo nautilus using a GUI, or use the terminal command

cd /usr/share/X11/xorg.conf.d/

sudo cp
xorg.conf.backup xorg.conf

On restart, the monitor settings should be remembered! (Tested on Ubuntu 13.04.)

removing overlay-scrollbar from default Ubuntu installation:

The selection zone to bring up the overlay scrollbar I have issues with. It appears when the cursor is over the left side of the window edge, but is displayed on the right. When moving the cursor to the right to manipulate the control, it often disappears - I find this frustrating.
Fortunately, it is easy to disable the "overlay scrollbars". On Ubuntu 12.04:

gsettings set
org.gnome.desktop.interface ubuntu-overlay-scrollbars false

and to bring them back:

gsettings reset
org.gnome.desktop.interface ubuntu-overlay-scrollbars

For Ubuntu 12.10 and 13.04, to disable them:

gsettings set
com.canonical.desktop.interface scrollbar-mode normal

and to bring them back:

gsettings reset
com.canonical.desktop.interface scrollbar-mode

The command should take effect immediately. Previously, I removed the package using "sudo apt-get remove overlay-scrollbar". While that worked, warnings would appear about the missing "overlay-scrollbar" GTK module when running applications.

fixing the fontconfig warning when running applications:

When running my Qt applications, under application output I would always see the message: Fontconfig warning: "/etc/fonts/conf.d/50-user.conf", line 9: reading configurations from ~/.fonts.conf is deprecated. This can be fixed by doing the following:

mkdir ~/.config/fontconfig

mv ~/.fonts.conf
~/.config/fontconfig/fonts.conf

The change should take effect immediately -- applications will no longer complain about it. (Tested on Ubuntu 13.04.)

setting up an environment for making documents with TeXworks and LaTeX:

On a new Ubuntu installation, to produce academic papers I install TeXworks software, the latexmk script, and some LaTeX packages, using the following:

sudo apt-get
install texworks latexmk texlive-latex-recommended
texlive-latex-extra

In TeXworks, Edit>Preferences>Typesetting. Add latexmk processing tool with the program usr/bin/latexmk and the following command line arguments:

-e

$pdflatex=q/pdflatex $synctexoption %O %S/

-pdf

$fullname

Check "view PDF after running", press OK. For default - set to latexmk.

switching between qt4 and qt5 with qtchooser:

I reinstalled Ubuntu 13.04 on a machine (comes with qt4) overtop a 13.10 installation (comes with qt5). I found when building through qtcreator that there were errors in relation to using the qt5 libraries rather than qt4. The program "qmake" is a symlink to the program "qtchooser", which was configured to use qt5. To set it back to qt4, the /usr/share/default.conf symlink needs to point to qt4.conf:

cd /usr/share/qtchooser

sudo rm default.conf

sudo ln -s qt4.conf
default.conf

open a terminal through nautilus:

Use the following command to install the extension:

sudo apt-get
install nautilus-open-terminal

youtube issues with chromium:

On an Ubuntu 12.04 installation with chromium, youtube videos often fail to load with the message "This video is currently unavailable". The fix (in my case):

sudo apt-get remove chromium-codecs-ffmpeg

sudo apt-get
install chromium-codecs-ffmpeg-extra

hostnames, avahi and .local:

You may find you are unable to connect using the hostname to another computer on the network (e.g. for a computer whose hostname is "whirringbox"):

ping whirringbox

ping: unknown host
whirringbox

Ubuntu (and others) include software called avahi, "zero-configuration networking software" which includes support for something called mDNS (or the "multicast Domain Name System"). On Ubuntu installations, there will be a program called avahi-daemon running. For example, if we run on whirringbox:

ps -ax | grep avahi

this displays

 684 ?        S      0:00 avahi-daemon: running
[whirringbox.local]

 687 ?        S      0:00 avahi-daemon: chroot
helper

8350 pts/0    S+   
 0:00 grep --color=auto avahi

The purpose of the avahi-daemon process is to make the computer accessible on the local network. Supporting mDNS, avahi-daemon waits for a message on the local network requesting the host with name "whirringbox.local" to identify itself. Then, the avahi-daemon replies to this message, providing the IP address of whirringbox. So in general, to connect to an Ubuntu machine by hostname for an mDNS-supporting system, you need to add ".local":

ping whirringbox.local

PING whirringbox.local (192.168.0.11) 56(84)
bytes of data.

64 bytes from whirringbox.local (192.168.0.11):
icmp_req=1 ttl=64 time=0.543 ms

64 bytes from whirringbox.local (192.168.0.11):
icmp_req=2 ttl=64 time=0.150 ms

64 bytes from
whirringbox.local (192.168.0.11): icmp_req=3 ttl=64 time=0.152 ms

I find this a great alternative to the idea of setting up static IP addresses and messing with /etc/hosts.

linker errors using webkitwidgets:

When attempting to add a webpage viewer to my Linux Qt5 application (Ubuntu 14.04) via a "QWebView", part of the "webkitwidgets" module (QT += webkitwidgets), I was missing some development libraries which were causing numerous linker errors (libraries which could not be found). Many related to gstreamer, but there were a few others. Installing the following few packages fixed this for me:

sudo apt-get install libgstreamer0.10-dev

sudo apt-get install libxslt-dev

sudo apt-get
install libgstreamer-plugins-base0.10-dev

convert a PDF into a series of images:

Use the command line utility pdftoppm:

pdftoppm -png
slides.pdf slide_imgs/slide

where -png defines the format (e.g. png, jpg) can be specified, slides.pdf is the input file, and slide_imgs/slide is the prefix for each filename (this puts slides into a slide_imgs subdirectory).

remove cached startup errors:

You may encounter some startup errors with a dialog saying "system program problem detected", even if nothing is actually wrong. These may be caused by errors that occurred long ago that have been not been cleared properly. To do this manually, use the following:

sudo rm
/var/crash/*

If you still have startup error dialogs after doing this, check the contents of the /var/crash directory.

Ubuntu Blog

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Usefull Linux Terminal Commands

aspell (command line spell checking)

apt/dpkg (package management, software installation)

cp/mv/rm (copy, move, delete files)

dd (clone a hard drive, backup drive to file)

df/du/find (drive usage)

ffmpeg (video transcoding, desktop recording, etc.)

gcc (creating software programs)

git (revision control system)

grep (search files for strings)

locate (search for files/directories)

man (software documentation)

mount (enabling access to drives/filesystems)

rsync (backups)

ssh (log into another machine)

tar/gzip (archive, compress)