Daily Commands
Commands I use often during normal Linux/RHEL work.
This page is for quick lookup. More detailed explanations can go into the other pages like Logs, Systemd, Networking, and Storage and LVM.
System information
Hostname and OS details
hostnamectl
RHEL version
cat /etc/redhat-release
Alternative:
cat /etc/os-release
Kernel version
uname -r
Uptime and load
uptime
Current user
whoami
User ID and groups
id
Disk and storage
Disk usage
df -h
Folder size
du -sh /path/to/folder
Example:
du -sh /var/log
List block devices
lsblk
Show filesystem UUIDs
blkid
Show mounted filesystems
mount
Cleaner view:
findmnt
Memory and CPU
Memory usage
free -h
Running processes
ps aux
Top processes
top
If available:
htop
CPU information
lscpu
Services
Check service status
systemctl status SERVICE_NAME
Example:
systemctl status sshd
Show failed services
systemctl --failed
Start service
sudo systemctl start SERVICE_NAME
Stop service
sudo systemctl stop SERVICE_NAME
Restart service
sudo systemctl restart SERVICE_NAME
Enable service at boot
sudo systemctl enable SERVICE_NAME
Disable service at boot
sudo systemctl disable SERVICE_NAME
Logs
Recent important logs
journalctl -xe
Logs from current boot
journalctl -b
Logs for a service
journalctl -u SERVICE_NAME
Example:
journalctl -u sshd
Follow service logs live
journalctl -u SERVICE_NAME -f
Last 100 system messages
sudo tail -n 100 /var/log/messages
Networking
Show IP addresses
ip a
Show routes
ip r
Show listening ports
ss -tulpn
Test ping
ping example.com
Test DNS
dig example.com
Alternative:
nslookup example.com
Test HTTP/HTTPS response
curl -I https://example.com
Trace route
traceroute example.com
If traceroute is not installed:
tracepath example.com
Users and login checks
Logged-in users
who
Recent logins
last
Failed logins
sudo lastb
Check user groups
id USERNAME
Files and permissions
List files
ls -lah
Find a file by name
find /path -name "filename"
Example:
find /etc -name "*.conf"
Search text inside files
grep -R "search_text" /path
Example:
grep -R "PermitRootLogin" /etc/ssh
Change owner
sudo chown USER:GROUP FILE_OR_FOLDER
Change permissions
chmod 755 FILE_OR_FOLDER
Package checks
Search package
dnf search PACKAGE_NAME
Package information
dnf info PACKAGE_NAME
Installed packages
rpm -qa
Search installed package
rpm -qa | grep PACKAGE_NAME
Which package owns a file
rpm -qf /path/to/file
Example:
rpm -qf /usr/bin/ssh
Quick first-check command set
When I do not know what is wrong yet:
hostnamectl
uptime
df -h
free -h
systemctl --failed
ip a
ip r
ss -tulpn
journalctl -xe
Notes
Add commands here that I use often but keep forgetting.