notes for Linux

Uptime: show the machine’s latest boot up time and running time. Can use to track when it restarted

difference between && and ; when executing shell commands:

using ; when the first command fails, the second command will still be executed

using && when the first command fails, the second command will not be executed

Change user accessibility of a file or directory: sudo chmod 777 /home/pi/schedule/sampleFile

When cannot press tab to auto-fill filenames:

Possible reason 1: root disk full, df –h will show this

Possible reason 2: lost writing access to /tmp. Check  /tmp access permissions, which should like this:

ls -l / |grep tmp

drwxrwxrwt   7 root root  4096 Nov  7 17:17 tmp

if current user does not have write access, then

sudo chmod a+rwxt /tmp

get system and hardware specs:

for command line solutions, you can use the command lshw.

Install it if needed:

sudo apt-get install lshw

then run something like

sudo lshw -html > mySpecs.html

then check the html file.

grep /  find something in many files:

grep  “variable1”  *.sh

xxx.sh   shell script

echo

ps aux | grep sensing

unsuccessfully make while son

then soff

then make install

~/.bashrc     shell shortcuts definition eg. Clrlog

After updating bashrc, need to use command: source .bashrc

check  all service status:

sudo service –status-all