Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
What are the difference between tail -f and tail -F?
Answer:
Basically these two command are very similar, except tail -F do one more thing: the retry.
This is useful when you are tailing a web server log, e.g. apache log. When the the log file got rotated, the tail -F will continue to work since it will retry for the rotated file, while tail -f can't.
Display the top 10 processes used up the most of the memory
Answer:
The following command display the most top 10 processes used up the most of the memory in your Linux system.
Example:
# ps aux | sort -nk +4 | tail
www-data 27972 0.0 2.8 253896 14916 ? S 13:10 0:00 /usr/sbin/apache2 -k start
www-data 27725 0.0 2.9 254028 15572 ? S 12:52 0:00 /usr/sbin/apache2 -k start
www-data 27912 0.0 2.9 253896 15660 ? S 13:06 0:00 /usr/sbin/apache2 -k start
www-data 27946 0.0 2.9 253764 15492 ? S 13:08 0:00 /usr/sbin/apache2 -k start
root 2710 0.0 3.1 252996 16444 ? Ss Dec08 1:20 /usr/sbin/apache2 -k start
www-data 27885 0.0 3.4 253508 18152 ? S 13:05 0:00 /usr/sbin/apache2 -k start
www-data 27892 0.1 6.7 261748 35472 ? S 13:06 0:00 /usr/sbin/apache2 -k start
www-data 27975 0.3 7.0 263036 37128 ? S 13:10 0:00 /usr/sbin/apache2 -k start
www-data 27964 0.7 8.2 268532 43452 ? S 13:09 0:00 /usr/sbin/apache2 -k start
mysql 2480 0.4 8.7 223920 46096 ? Sl Dec08 21:07 /usr/sbin/mysqld
Since the apache2 was configured to run in the prefork mode, so you see multiple apache processes there.
List the size of sub directories in the current directory
Answer:
To check the disk usage of all sub directories in the current directory, you can try the following method:
# sudo du -h --max-depth=1
4.0K ./src
341M ./lib
68M ./bin
24K ./games
195M ./share
36M ./local
18M ./sbin
18M ./include
673M .How to kill and logout a logged in user
Answer:
Assume john is logged in and you want to terminate his session, you can use the skill command.
# sudo skill -KILL -u john
Extract a bzipped tar file
Answer:
Normally tar is combined with gzip as the most common usage, however, sometimes people use bzip2 instead for maximum compression rate. File in such format usually have the file name like: program.tar.bz2
To extract it using a single command:
# tar -jxvf program.tar.bz2
The key is the argument - j
