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show the free space on all filesystems | df -h |
lists the name and pids of the top 5 processes by percentage of CPU usage | ps -eo pid,comm,%cpu --sort=-%cpu | head -n 6 |
shows how much free memory a system has | free -h |
shows how much free space there is on the root filesystem | df -h / |
shows the disk space used by the directory /var/log | du -sh /var/log |
show the last date and time the system was rebooted | who -b |
show how long the system has been up | uptime -p |
who is currently logged into the system | who |
install wget on Redhat without user input | yum install -y wget |
set my user's time zone to Los Angeles | timedatectl set-timezone America/Los_Angeles |
show the version of the kernel | uname -r |
show the version of the operating system | cat /etc/os-release |
find the largest file under my home directory | find ~ -type f -exec ls -lh {} + | sort -k 5 -hr | head -n 1 |
make data.dat readable by just the owner | chmod 400 data.dat |
set the file creation mask so that only the owner has file write permission | umask 037 |
create a new file called data.dat with a size of 512K bytes | truncate -s 512K data.dat |
create an ext3 filesystem in my existing file named disk.img | mkfs.ext3 disk.img |
set the system's timezone to Los Angeles | timedatectl set-timezone America/Los_Angeles |
create a new group called alfa | groupadd alfa |
add user test to the group called alfa | usermod -aG alfa test |
add user test to the alfa group as administrator | usermod -aG alfa test; gpasswd -A test alfa |
remove the group password from the alfa group | gpasswd -r alfa |
restrict access of all users in the group named alfa | chmod -R o-rwx /path/to/directory |
remove user test from the alfa group | gpasswd -d test alfa |
remove the alfa group | groupdel alfa |
add a new user named test | adduser test |
add a login for a new user named test which expires 90 days from today | useradd -e $(date -d "+90 days" +%Y-%m-%d) test |
give me the date 90 days from today | date -d "+90 days" |
create a new systems group called alfa2 | groupadd alfa2 |
lock user test2's account | usermod -L test2 |
force user test2 to change their password at next login | chage -d 0 test2 |
modify the access time of my file data.dat to be 12:00 on 2022-12-31 | touch -a -t 202212311200 data.dat |
create a FIFO named myfifo in /tmp | mkfifo /tmp/myfifo |
insert #!/usr/bin/python3 at the top of each *.py files under the current directory | for file in *.py; do sed -i '1i #!/usr/bin/python3' "$file"; done |
rename all of my files named test.py replacing the string test with unit_test | find . -type f -name 'test.py' -execdir mv {} unit_test.py \; |
prefix every non-blank line in file.log with the string 'hello' | sed '/./ s/^/hello/' file.log |
change the file extension from .mpg to .avi every file in directory /home/test/uploads | for file in /home/test/uploads/*.mpg; do mv "$file" "${file%.mpg}.avi"; done |
prefix the line number to every line in file.log | nl -ba file.log |
make the file pretty-print.sh executable | chmod +x pretty-print.sh |
append all PNG and JPG files to the existing tar archive file images.tar | tar -rf images.tar *.png *.jpg |
calculate the md5 checksum of every file under the directory named downloads | find downloads -type f -exec md5sum {} + |
change the group ownership to alfa of my file named download.dat | chgrp alfa download.dat |
count all of the directories under my home directory | find ~ -type d | wc -l |
list the *.dat files in the current directory in ascending order by size | ls -lS --block-size=1 --reverse *.dat |
create the path src/vpd/new without an error if the path already exists | mkdir -p src/vpd/new |
list all files in my Downloads directory which have not been accessed within the last 3 weeks | find ~/Downloads -type f -atime +21 |
count the total number of lines in the *.c files under my src directory | find src -name "*.c" -type f -exec wc -l {} + | awk '{total += $1} END {print total}' |
find all *.c and *.h files under the src directory containing the pattern TODO and print just the file names | grep -lR "TODO" src --include \*.c --include \*.h |
show the fully-qualified domain name of my host | hostname -f |
calculate the number of days between the dates Jan 12, 2023 and Jan 20, 2024 | echo $(( ($(date -d "Jan 20, 2024" +%s) - $(date -d "Jan 12, 2023" +%s)) / 86400 )) |