Essential Linux Commands Every Operations Engineer Should Master

As an operations professional, mastering these common Linux commands can dramatically improve work efficiency.

1. Files and Directories

cd – change directory

cd /home            # enter /home directory
cd ..               # go up one level
cd ../..            # go up two levels
cd                  # go to home directory
cd ~user1           # go to user1's home
cd -                # return to previous directory

pwd – display current path

# pwd
/root

ls – list files and directories

ls                # list names
ls -l             # detailed list
ls -a             # include hidden files
ls -R             # recursive list
ls [0-9]          # names containing digits

cp – copy files

-a  copy attributes
-p  preserve attributes (useful for backup)
-i  prompt before overwrite
-r  recursive copy (directories)
-u  copy only when source is newer

mv – move or rename files

-f  force overwrite
-i  prompt before overwrite
-u  overwrite only if source is newer

rm – remove files or directories

-f  ignore nonexistent files
-i  interactive prompt
-r  recursive delete (dangerous for directories)

2. Viewing File Contents

cat, tac, more, head, tail and their options

cat file1               # view from start
tac file1               # view from end
cat -n file1            # show line numbers
more file1              # paginate long file
head -n 2 file1         # first two lines
tail -n 2 file1         # last two lines
tail -n +1000 file1    # from line 1000 onward
cat file1 | head -n 3000 | tail -n +1000   # lines 1000‑2999

3. File Search

find, whereis, which

find / -name file1                # search from root
find / -user user1               # files owned by user1
find /usr/bin -type f -atime +100   # executable not accessed in 100 days
find /usr/bin -type f -mtime -10    # created/modified in last 10 days
whereis halt                     # locate binary, source, man
which halt                       # full path of executable

Delete files larger than 50 M

find /var/mail/ -size +50M -exec rm {} \;

4. Permissions

chmod – change mode

ls -lh                     # view permissions
chmod ugo+rwx directory1   # grant rwx to user, group, others
chmod go-rwx directory1    # remove rwx from group and others

chown – change owner

chown user1 file1               # change owner
chown -R user1 directory1       # recursive ownership change
chown user1:group1 file1        # change owner and group

chgrp – change group

chgrp group1 file1

5. Text Processing

grep – filter lines

grep Aug /var/log/messages                # lines containing "Aug"
grep ^Aug /var/log/messages               # lines starting with "Aug"
grep [0-9] /var/log/messages              # lines with digits
grep Aug -R /var/log/*                    # recursive search

sed – stream editor

sed 's/string1/string2/g' example.txt   # replace all occurrences
sed '/^$/d' example.txt                # delete empty lines

paste – merge files side by side

paste file1 file2
paste -d '+' file1 file2

sort, uniq – sort and deduplicate

sort file1 file2
sort file1 file2 | uniq          # unique lines
sort file1 file2 | uniq -u       # lines only in one file
sort file1 file2 | uniq -d       # common lines

comm – compare two sorted files

comm -1 file1 file2   # exclude file1 lines
comm -2 file1 file2   # exclude file2 lines
comm -3 file1 file2   # only common lines

6. Archiving and Compression

tar – create, list, extract archives

-c  create
-t  list contents
-x  extract (use -C to specify directory)
-j  use bzip2
-z  use gzip
-v  verbose
-f  archive file name
-C  change to directory

Other tools

bunzip2 file1.bz2
bzip2 file1
gunzip file1.gz
gzip file1
gzip -9 file1          # maximum compression
rar a file1.rar test_file
rar a file1.rar file1 file2 dir1
rar x file1.rar
zip file1.zip file1
unzip file1.zip
zip -r file1.zip file1 file2 dir1

7. System Shutdown, Reboot, Logout

shutdown -h now          # halt now
init 0                  # halt (method 2)
telinit 0              # halt (method 3)
shutdown -h hh:mm      # schedule halt
shutdown -c            # cancel scheduled halt
shutdown -r now        # reboot now
reboot                 # reboot (method 2)
logout                 # log out
time command           # measure execution time

8. Process Management

jps – list Java processes

ps – snapshot of processes

-A  all processes
-a  without controlling terminal
-u  user-oriented
-x  together with -a for more info
-l  long format
ps aux      # all processes detailed
ps ax       # without terminal
ps -lA      # long format all
ps axjf     # process tree

kill – send signals

kill -l                     # list signals
kill -9 3268                # force kill PID 3268

killall – kill by name

killall nginx
killall -9 bash
killall -TERM nginx

top – interactive performance monitor

netstat – view listening ports netstat -tunlp | grep <port> Original source: https://www.jianshu.com/p/7c0df6fcfc71