My personal quicklist of Linux server commands.
Just FYI, these commands are mostly for Apache/LiteSpeed servers on CentOS. I don’t do as much stuff with NGINX and Ubuntu. Will add more over time.
OS:
hostnamectl
– see operating system and version, reference linkhostname
– see hostnamehostname server.domain.com
– change hostname to any desired domainwhoami
– shows your user name (useful for knowing if you’re executing commands as root user or another user)su
,su -
,sudo -i
– switch to root user if you haven’t already. “su -” is probably more proper since it creates a login shell with new environment.passwd
– change password for current userlogout
– log out of current useryum update
– update server packages (useful before doing new software installs)- Auto completion – hit the [TAB] key while typing commands to auto complete names of directories and files.
SSH:
- Connect to ssh
ssh user@ip -p 2222
(the-p
and port number isn’t needed if using default port 22) /etc/ssh/sshd_config
– editing SSHD, changing SSH port number, allowing/disabling SSH or password authenthication, etc.- getting SSH port
grep Port /etc/ssh/sshd_config
(may need “sudo” in front) systemctl restart sshd.service
– restart sshd. Link.cat ~/.ssh/authorized_keys
– lists authorized SSH keys, add more public SSH keys here to give access other admins or support staff. The location might also be/root/.ssh/authorized_keys
.
SSH key – generate on Macbook terminal:
- generate SSH key
ssh-keygen -t rsa
- choose private key save location or leave empty for default
/Users/username/.ssh/id_rsa
, choose passphrase for private key if you want (I usually leave empty) cat /Users/username/.ssh/id_rsa.pub
to see public key, copy and import it to where you need. TIP: sometimes when copying off the command line, it adds line-breaks that you need to delete when pasting elsewhere.ssh-add /Users/user/.ssh/id_rsa
to load private key in terminalssh-keygen -R 123.123.123.123
– solves the “known host issue” by removing a known host. Useful for when you rebuild a server but keep the same IP.
SSH key – generate on Linux:
- generate SSH key
ssh-keygen -t rsa -b 4096
, and press enter through all the prompts (about 3). cat /root/.ssh/id_rsa.pub
to see public key.cat /root/.ssh/id_rsa
to see private key.
Navigating around command line (full guide):
ls
,ls -a
– list files in directory, usels -S
to sort by size orls -Sr
to reverse order, show hidden filesls -l
– list files but also show permissions, # of hardlinks, file owner and group, size and modification time. You can combine togetherls -la
ls *.php
– lists only files with .php extension.cd
– goes to user home directory.cd /
– goes to root directory.cd
orcd ~
goes to user home directory (of whichever user is logged in).cd
returns to default working directory in linux (ideally, the root but often not the case)cd [directoryname]
is relative whereascd /directory
is absolutecd ..
– goes up to parent directorycd -
– goes to previous directorypwd
– shows path to current directoryclear
or CTRL+L to clear the screen
Files & Directories (create, delete, move, copy, archive):
mkdir test
– make directory called “test”,rmdir test
removes itrm test
– delete file or directory called “test”rm -rf test
– deletes “test” directory without prompting you for every filerm -rf *test*
– deletes all files/directories with the string “test” in the name.rm -fv *.txt
removes all files in current directory with “.txt” extension.find . -name *.ext -type f -delete
deletes all files with “ext” extension including within subdirectories. Other options.cp test /location
– copy “test” file or directory to “/location” directory. Other options.cp oldname.txt newname.txt
copies file to new name in same directory.'cp' -R -rf file location
use this to do recursive overwrite without any prompt.cp -avr /path/dir1 /path/dir2
copies one directory (and contents) to another.mv test /location
– move “test” to “/location” directory. Usemv -f
to force overwrites. Other options.mv oldname.txt newname.txt
– renames the file.mv
command also used for renaming directories as well.tar -czvf folder.tar.gz folder
– archive “folder” directory into folder.tar.gz file. Other compression commands.tar -xzvf folder.tar.gz
– extract archive in current working directory. Other options.gzip -d database.sql.gz
– extract sql.gz files.zip -r folder.zip folder
archives the “folder” directory into zip format. You don’t actually need to put “.zip” but I find it makes the command easier to remember. (Don’t forget the-r
option as it makes the command recursive and includes every file within subdirectories as well.)unzip folder.zip
unzips archive to current directory.- Hide files and show hidden files
Files & Directories (ownership, permissions):
- Change file ownership –
chown USER:GROUP FILE
orchown -R USER:GROUP FILE
for recursive. Useful after migrating files from another server and they don’t work. Another link. chmod -R 755 /path/to/file.php
changes that file permission to 755. For more explanations about change permissions and recursively change permissions (symbolic vs numeric method).find /path/to/dir -type d -exec chmod 755 {} \;
andfind /path/to/dir -type f -exec chmod 644 {} \;
are much betters ways to recursively set all directory permissions to 755 and file permissions to 644 (as common web practice).- save command output to a file https://askubuntu.com/questions/420981/how-do-i-save-terminal-output-to-a-file
Files (searching & hack detection):
grep -r "string" /home/user
– (recursively) searches all instances of “string” for all files within/home/user directory
. Can also dogrep -r -l 'pattern' /path/to/dir
to list only the files.find /home/user -type f -name "something.php"
– searches/home/user
directory for all files named “something.php”.find /home/user -type f -ctime -7
– searches all files within/home/user
directory changed within 7 days or less. (Change to + sign if you want to search for changes older…usually uncommon.)find /home/user -type f -name "*.php" -ctime -30
– finds all files with .php extension changed within past 30 days. More find examples.find /etc -type f -printf '%TY-%Tm-%Td %TT %p\n' | sort
– finds most recently changed files, listed in order of less recent to most recent. More find examples.zgrep -Eo "string" /path/to/gzippedfile.gz
– searches for the text “string” within an archive.find . -type f | wc -l
– counts number of total files in current directory and subdirectories
File Transfer:
wget https://address.com/to/file.zip
– download external file to current working directorycurl -0 https://addres.com/to/file.zip
can also work if wget doesn’t (other alternatives to wget)rsync -a [email protected]:/remote/dir /local/dir
copies (pulls) remote directory to local directory.rsync -a /local/dir [email protected]:/remote/dir
copies (pushes) local directory to remote directory.rsync -avz --rsh='ssh -p2220' /local/dir [email protected]:/remote/dir
pushes to remote site using specified ssh port 2220.sftp user@IPorhostname:/path/to/file /local/dir
downloads remote file via SFTP to specific directory. This command will ask you for SFTP password. Can also try this command with “scp -r” instead of “sftp” if you need recursive copy.
SFTP:
sftp user@serverIP_or_hostname
– do this from destination server. (Usesftp -oPort=1234 user@serverIP_or_hostname
if there’s a custom SFTP port other than 22.)- Use
cd
andls
commands to navigate around the remote computer. get filename.zip
– to download file local.- Reference link
VI text editor:
vi filename.txt
– open any file up in vi editorpress[ESC]
– to switch to normal mode:i
– insert (editing mode)dd
(from normal mode) – deletes the line under cursor. Other delete commands.:q!
– quit without saving:wq
– quit with savingcat /path/to/file
– prints the file.cat /path/to/file | more
– prints file but showing full lines.grep database wp-config.php
– prints only lines with the string “database” in wp-config.php.grep -A 1 "database" wp-config.php
– prints all lines with “database” (but also INCLUDING 1 line after). Can use-B 1
to show 1 line before, or-C 1
to show both one line before and after.
Disks, usage & space:
- Check available space –
df
(default),df -h
(friendly KB/MB/GB format),df -l
(local size only) du -sh *
– check sizes within current directorydf -k
df -k /tmp
– checks free space of “/tmp” directorysudo du -a /home/ | sort -n -r | head -n 20
– lists largest files in “/home” directory.- find large files
- mount
- unmount –
umount /path/to/mount
(removes from /etc/fstab) - view mounts –
cat /etc/fstab
- disk space commands and more du commands
du -hsx /* | sort -rh | head -10
Ports:
- Check for listening ports
sudo lsof -i -P -n | grep LISTEN
Processes:
- kill processes –
pkill 12345
, replacing “12345” with actual process ID
Databases (MySQL & MariaDB):
- restart MariaDB –
systemctl start mariadb
- export (aka “dump”) mysql database into a file –
mysqldump -u dbuser -p dbname > dbfile.sql
, you will be prompted for password - import sql file into db (assuming db’s and users already created) –
mysql -u dbuser -p dbname < dbfile.sql
, you will be prompted for password. (Add-f
flag after the “-p” to force an import to skip errors.) cat /root/.my.cnf
– recover mysql root pass, or reset it- managing databases and users from SSH, nice video and explanation
- creating databases and users from SSH
- curious about trying non-default mysql configs? Try this.
MySQL commands (for MySQL/MariaDB shell/prompt):
mysql -u user -p
logs you in,exit
logs you outSHOW DATABASES;
list all databasesCREATE DATABASE database_name;
– creates DBDROP DATABASE database_name;
– drops DBSELECT user, host FROM mysql.user;
– list all DB usersCREATE USER 'database_user'@'localhost' IDENTIFIED BY 'user_password';
– creates DB userDROP USER 'database_user'@'localhost';
– deletes DB userGRANT ALL PRIVILEGES ON database_name.* TO 'database_user'@'localhost';
– grant all privileges to specified user for specified databaseGRANT ALL PRIVILEGES ON *.* TO 'database_user'@'localhost';
– grant all privileges to specified user for all databasesREVOKE ALL PRIVILEGES ON database_name.* TO 'database_user'@'localhost';
– revoke privilegesSHOW GRANTS FOR 'database_user'@'localhost';
– see all user privilegesshow global variables like 'log_error'
– show location of error log file.
LiteSpeed web server:
- installing LS
- reset LS console pass –
cd /usr/local/lsws/admin/misc
and then./admpass.sh
- version check –
/usr/local/lsws/bin/lshttpd -v
- start LS –
/usr/local/lsws/bin/lswsctrl start
- restart LS –
/usr/local/lsws/bin/lswsctrl reload
- upgrade OLS –
yum update', then 'yum upgrade openlitespeed
- enable crawler (cPanel) –
vi /etc/apache2/conf.d/includes/pre_main_global.conf
and add - view logs
/tmp/lshttpd/.status
- More LS license commands
WHM/cPanel:
- refresh disk quota
- license check
- force run backups –
/usr/local/cpanel/bin/backup --force
(more info) - update WHM
/scripts/upcp
or/scripts/upcp --force
(if it’s already updated) - Reset max deferred email limit – delete `rm /var/cpanel/email_send_limits/max_deferfail_thedomain.com`
CyberPanel:
- Error logs –
cat /home/cyberpanel/error-logs.txt
(log files on CyberPanel) - Cron schedules –
/etc/crontab
clear out unnecessary cronjobs eating up server resources (backups)
Security:
- CSF firewall – CSF firewall installation and basic commands
- opening port 1234 –
iptables -I INPUT -p tcp --dport 1234 -j ACCEPT
- closing ports 111 –
iptables -I INPUT 1 -m tcp -p tcp --dport 111 -j DROP
,iptables -I INPUT 1 -m udp -p udp --dport 111 -j DROP
sudo dmesg -n 1
– disable annoying kernel messages- Security log-scanning commands, please see Recovering from HACKED server
Firewalld:
systemctl status firewalld
– check statussystemctl start firewalld
– start itsystemctl enable firewalld
– enables itfirewall-cmd --list-all
,firewall-cmd --list-ports
– see open ports, alternate:for s in firewall-cmd --list-services; do firewall-cmd --permanent --service "$s" --get-ports; done;`
- open port,
firewall-cmd --permanent --add-port=1234/tcp
(using whichever port number you need) , thenfirewall-cmd --reload
systemctl stop firewalld
– stops itsystemctl disable firewalld
– disables it
Configuration files (common locations):
Logs (locations and common commands):
tail /location/of/log
shows last 10 lines of log filetail -n 100 /location/of/log
shows last 100 linestail -f /location/of/log
keeps watching last 10 lines of log file- You can also use “less +F” (but generally not for big files)
grep "abc" /file/name
to find lines with the string “abc” in them. See other grep examples.
Disks (format, partition, mount):
df -Th
show mounted disks/partitions and file systemslsblk
show attached storage disks- Partition & format disk –
sudo fdisk /dev/diskname
replace “diskname” with what you want (usually sda1/vdb1). From partition command line,n
follow defaults, thena
to make it bootable (if needed),p
to check that it partitioned correctly, andw
to write these partition changes. Trylsblk
afterwards to check everything worked. sudo mkfs.ext4 /dev/partitionname
partition name is usually disk name with a partition number (sda1, sda2, etc). You can also switchext4
file system to something else likexfs
.- Mount new disk –
sudo mkdir /disk1
to create new “disk1” directory in your root (use another name if you want).sudo mount /dev/partitionname /disk1
mounts partition to the directory. - https://upcloud.com/community/tutorials/adding-removing-storage-devices/ for more info on automatically mounting at boot, etc.
Scripts:
bash scriptname.sh
to run the script,sh scriptname.sh
is another option
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