Table of Content
Weight: 4
Description: Candidates should be able to use the basic Linux commands to manage files and directories.
Key Knowledge Areas:
- Copy, move and remove files and directories individually
- Copy multiple files and directories recursively
- Remove files and directories recursively
- Use simple and advanced wildcard specifications in commands
- Using find to locate and act on files based on type, size, or time
- Usage of tar, cpio and dd
Terms and Utilities:
cp find mkdir mv ls rm rmdir touch tar cpio dd file gzip gunzip bzip2 xz file globbing
pwd
pwd command same as $PWD env variable echo $PWD ls $PWD
ls
ls -al # long format d directory - regular file l symbolic link b block device c char device ls -i # inode ls -lS # sort by size bytes ls -ltr # reserve sort by mtime
cp , mv , rm
cp -b | --backup source targetdir # create backup before copy cp -p s1 t1 # preserve attributes like owner:group mkdir -p dir1/dir2/dir3 rm -r dir1 # delete all dir1/dir2/dir3/*
globbing
wildcard
~ /home/user or /root (the user's home directory) echo ~/.bashrc
* Any sequence of characters (or no characters) echo /etc/*ost*
? Any one character echo /etc/hos?
[abc] Any of a, b, or c echo /etc/host[s.]
{abc,def,ghi} Any of abc, def or ghi. echo /etc/hosts.{allow,deny}
touch
touch -t 201511032200.59 file touch -d 11am file date -r f1 # save refer file f1 touch -r f1 f1a # create new f1a refer f1 timestamp mtime modify time atime access time
find
find . -size 0
find . -size -26c -size +23c -exec ls {} \; # size >=23 bytes and = 60 mins,
file
oldhorse@dclab-u1504s:~$ file test2 test2: ASCII text oldhorse@dclab-u1504s:~$ file -i test2 test2: text/plain; charset=us-ascii
gzip
gzip -N filename # generate filename.gz and preserved name , timestamp gzip -d filename.gz
bzip2
bzip2 file bzip2 file.bz2 bzcat # same as bzip2 -dc , view inside bz2 without decompressed bzip2recover # recover data from damaged zip2 file
tar
tar -zcvf file.tar files tar -tvf file.tar
xz
tar -cJf backup.xz backup/ tar -tJf backup.xz tar -xJf backup.xz
cpio
find backup/ -depth -print0 | cpio --null -o > backup.cpio # cpio using absolute filename cpio -i --list "*backup*"
dd
dd if=test1 of=test2 # copy test1 to test2 dd if=test1 conv=ucase dd if=/dev/sda2 of=backup-1 sudo dd if=/dev/sda2 of=backup-sda2 # backup partition sudo dd if=/dev/sda2 |gzip > backup-sda2.gz gunzip backup-sda2.gz -c | dd of=/dev/sda7 # restore to partition dsa7
Quiz questions
1. What is the parameter for copy, move and remove that requests confirmation from the terminal before acting? 2. Who is the owner of a file created using touch? 3. Which parameter for copy will cause it to copy file permissions and ownership as far as possible? 4. How do you find files which have not been modified for more than 2 days? 5. How do you find executable files which have the set-gid bit set?
Answers to quiz questions
1. -i 2. The user that ran the command. 3. -a 4. find -mtime +2 5. find -type -f perm 2001