umount detaches a mounted filesystem from the Linux directory tree. It is commonly used for USB drives, external disks, network mounts and temporary mount points. Check mounted filesystems Unmount by mount point This unmounts the filesystem currently attached at /mnt/backup. When the device is busy If unmounting fails with a busy message, check which process … Read more
A legacy note on hard disk performance tuning and why old hdparm flags should be used carefully today.
A safer short note on using fsck to check Linux filesystems and why device selection matters.
chkconfig was commonly used on older Linux distributions to view and manage which services start at different runlevels. On many modern systems, systemctl has replaced it. List service settings Modern systemd equivalent Use chkconfig mainly when working with older Red Hat, CentOS or similar systems that still use the older service model.
The printenv command prints environment variables for the current shell session. These variables can affect paths, language settings, application configuration and script behaviour. Show all environment variables Show one variable This is useful when troubleshooting scripts that behave differently for different users or services.
Modern notes on shred, secure file deletion, SSD wear levelling, snapshots, encryption, and device sanitisation.
Practical Linux rootkit-checking notes covering chkrootkit, rkhunter, logs, package verification, and safer recovery after a suspected compromise.
The md5sum command calculates an MD5 checksum for a file. It is useful for basic file comparison, but it should not be used for modern security-sensitive verification. Create a checksum Save and check a checksum For stronger verification, prefer SHA-256 checksums when they are available.
Linux can read and write NTFS drives using the NTFS driver available in modern distributions. This is useful when accessing Windows partitions or external drives. Identify the device Confirm the device name and filesystem type before mounting. Do not guess device names. Create a mount point Mount the NTFS drive Replace /dev/sdXN with the correct … Read more
sum prints a simple checksum and block count for a file. It is an older utility and is mostly useful when working with legacy scripts or older Unix-style examples. Check a file For modern file verification, prefer stronger tools such as sha256sum where available.