ubuntu +crontab+grub

for upgrade error subprocess

try this first

sudo apt-get remove linux-image-3.xxx-generic

if not work try this

sudo rm -rf /var/lib/dpkg/updates/*

sudo rm -rf /var/lib/apt/lists/* sudo rm /var/cache/apt/*.bin sudo apt-get clean sudo apt-get autoremove sudo apt-get update sudo dpkg --configure -a sudo apt-get install -f

if still getting same error then try

sudo dpkg --remove --force-remove-reinstreq package_name

after removing package update your system and restart once

if boot option menu disappear

sudo add-apt-repository ppa:yannubuntu/boot-repair sudo apt-get update sudo apt-get install -y boot-repair && (boot-repair &)

if boot partition full

sudo apt-get autoremove

speedup ubuntu

sudo apt-get install linux-firmware-nonfree

Click on the grey Ubuntu logo (Dash home). Query:software

Click on Software & Updates - tab Additional Drivers.

sudo apt-get install synaptic dconf-tools gksu gdebi lxkeymap inxi leafpad

cat /proc/sys/vm/swappiness

changevalue 60 to 10

gksudo leafpad /etc/sysctl.conf

add line

# Decrease swap usage to a more reasonable level

vm.swappiness=10

restart

cat /proc/sys/vm/swappiness

1 GB RAM or more: swappiness at 10

Less than 1 GB RAM: swappiness at 5

install youtube-dl

wget: sudo wget https://yt-dl.org/downloads/2014.09.25/youtube-dl -O /usr/local/bin/youtube-dl sudo chmod a+x /usr/local/bin/youtube-dl sudo youtube-dl -U

$ sudo apt-get install python-pip python-dev build-essential $ sudo pip install --upgrade pip $ sudo pip install --upgrade virtualenv sudo pip install --upgrade youtube-dl

install ffmpeg in ubuntu 14.04

sudo add-apt-repository ppa:mc3man/trusty-media sudo apt-get update sudo apt-get install ffmpeg gstreamer0.10-ffmpeg

//sudo add-apt-repository ppa:jon-severinsson/ffmpeg

//sudo apt-get update //sudo apt-get install ffmpeg //sudo apt-get install frei0r-plugins

convert mp4 to mp3

sudo add-apt-repository ppa:ffmulticonverter/stable sudo apt-get update sudo apt-get install ffmulticonverter

sudo apt-get install format junkie

edit grub boot order

sudo gedit /etc/default/grub

and edit GRUB_DEFAULT=0

install flash

sudo apt-get install ubuntu-restricted-extras

install flash on ubuntu 14.04 64 bit

sudo apt-get install pepperflashplugin-nonfree sudo update-pepperflashplugin-nonfree --install

menu bar time disappear

Try reseting its configuration

dconf reset -f /com/canonical/indicator/datetime/

If it didn't show up try kill it, it should restart

pkill -f datetime

switch language in ubuntu 13.10

sudo add-apt-repository ppa:attente/modifier-only-input-switch sudo apt-get update sudo apt-get upgrade

sudo add-apt-repository ppa:attente/1218322

sudo apt-get update

sudo apt-get upgrade

Install font thai on ubuntu

1. ใช้คำสั่ง sudo apt-get update เพื่ออัปเดต packages

2. ใช้คำสั่ง sudo apt-get install ttf-thai-tlwg xfonts-thai xfonts-thai-etl xfonts-thai-manop xfonts-thai-nectec xfonts-thai-poonlap xfonts-thai-vor เพื่อติดตั้ง font thai ที่มีคนคิดขึ้นมา

3. ใช้คำสั่ง sudo apt-get install msttcorefonts เพื่อติดตั้ง font ของไมโครซอฟต์

หากเป็นฟอนต์ที่มีคนสร้างขึ้นมาเองในรูปแบบไฟล์ *.ttf มีขั้นตอนดังนี้

1. สร้างไดเรกทอรี ~/.fonts แล้วคัดลอกไฟล์ *.ttf มาไว้ในไดเรกทอรีนี้

2. แก้ไขไฟล์ ~/.fonts.conf โดยให้มีการ match ของฟอนต์ เช่น

3. รันคำสั่ง fc-cache -f -v

crontab

Crontab file consists of command per line and have six fields actually and separated either of space or tab. The beginning five fields represent time to run tasks and last field is for command.

- Minute (hold values between 0-59)
- Hour (hold values between 0-23)
- Day of Month (hold values between 1-31)
- Month of the year (hold values between 1-12 or Jan-Dec, you can use first three letters of each month’s name i.e Jan or Jun.)
- Day of week (hold values between 0-6 or Sun-Sat, Here also you can use first three letters of each day’s name i.e Sun or Wed. )
- Command

1. List Crontab Entries

List or manage the task with crontab command with -l option for current user.

# crontab -l 00 10 * * * /bin/ls >/ls.txt

2. Edit Crontab Entries

To edit crontab entry, use -e option as shown below. In the below example will open schedule jobs in VI editor. Make a necessary changes and quit pressing :wq keys which saves the setting automatically.

# crontab -e

3. List Scheduled Cron Jobs

To list scheduled jobs of a particular user called tecmint using option as -u (User) and -l (List).

# crontab -u tecmint -l no crontab for tecmint

Note: Only root user have complete privileges to see other users crontab entry. Normal user can’t view it others.

4. Remove Crontab Entry

Caution: Crontab with -r parameter will remove complete scheduled jobs without confirmation from crontab. Use -i option before deleting user’s crontab.

# crontab -r

5. Prompt Before Deleting Crontab

crontab with -i option will prompt you confirmation from user before deleting user’s crontab.

# crontab -i -r crontab: really delete root's crontab?

6. Allowed special character (*, -, /, ?, #)

- Asterik(*) – Match all values in the field or any possible value.
- Hyphen(-) – To define range.
- Slash (/) – 1st field /10 meaning every ten minute or increment of range.
- Comma (,) – To separate items.

7. System Wide Cron Schedule

System administrator can use predefine cron directory as shown below.

- /etc/cron.d
- /etc/cron.daily
- /etc/cron.hourly
- /etc/cron.monthly
- /etc/cron.weekly

8. Schedule a Jobs for Specific Time

The below jobs delete empty files and directory from /tmp at 12:30 am daily. You need to mention user name to perform crontab command. In below example root user is performing cron job.

# crontab -e 30 0 * * * root find /tmp -type f -empty -delete

9. Special Strings for Common Schedule

Need to replace five fields of cron command with keyword if you want to use the same.

10. Multiple Commands with Double amper-sand(&&)

In below example command1 and command2 run daily.

# crontab -e @daily <command1> && <command2>

11. Disable Email Notification.

By default cron send mail to user account executing cronjob. If you want to disable it add your cron job similar to below example. Using >/dev/null 2>&1 option at the end of the file will redirect all the output of the cron results under /dev/null.

[root@tecmint ~]# crontab -e * * * * * >/dev/null 2>&1

conclusion: Automation of tasks may help us to perform our task better ways, error free and efficiently. You may refer manual page of crontab for more information typing ‘man crontab‘ command in your terminal.