chmod calculator
Convert between 755, rwxr-xr-x and checkboxes, and copy the chmod command.
Fix it on Linux
Paste the error, find the cause, copy the command that fixes it. Tested fixes for Ubuntu, Debian, Fedora, Arch and Linux Mint.
Try: unable to locate package, no sound, grub rescue, chmod 755
Most-searched error messages
E: Unable to locate packageerror: externally-managed-environmentE: Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 1234 (apt)No space left on devicePermission denied (publickey).permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sockfatal: detected dubious ownership in repository atTemporary failure in name resolutionuser is not in the sudoers file. This incident will be reported.E: Unable to correct problems, you have held broken packages.
Free tools
Cron to systemd timer
Turn a crontab line into a .service and .timer pair with the right OnCalendar=.
Crontab generator
Build cron expressions, explain them in plain English and preview the next run times.
Subnet calculator
Network, broadcast, host range, netmask and host count for any IPv4 CIDR block.
umask calculator
Turn a umask into file and directory modes, or find the umask for the mode you want.
Common problems, fixed step by step
NVIDIA black screen fix
Get past the black screen, find out why the NVIDIA module failed, and reinstall the right driver.
grub rescue> fix
Boot from the grub rescue> prompt, then reinstall GRUB properly from a live USB (UEFI and BIOS).
No sound / Dummy Output
Dummy Output, muted channels, HDMI audio and missing SOF firmware with PipeWire and WirePlumber.
Bluetooth not working
rfkill, bluetooth.service, firmware, pairing failures and headset audio, with commands for every distro.
Fix Wi-Fi Not Working on Linux
Fix Wi-Fi not working on Linux: identify the adapter, check rfkill, install drivers and firmware, and fix NetworkManager on Ubuntu, Fedora and Arch.
Touchpad not working
Dead or disabled touchpad, tap-to-click, i2c_hid and PS/2 issues, GNOME, KDE and X11 settings.
Ubuntu slow boot
Measure boot with systemd-analyze, then fix wait-online, fstab and swap timeouts, and other slow units.
Remove Ubuntu from dual boot
Uninstall Ubuntu from dual boot: boot order, EFI entry, partitions, and repairing Windows boot if needed.
After installing Ubuntu 26.04
Updates, drivers, codecs, Flatpak, firewall, backups and GNOME tweaks for a fresh Ubuntu 26.04.
Browse by section
Errors50 pagesExact Linux error messages, what causes them and the command that fixes them.Fixes & guides58 pagesStep-by-step fixes for hardware, boot and desktop problems, plus install and upgrade walkthroughs.Cheat sheets20 pagesOne-page command references with the options people actually use.Tools5 pagesSmall in-browser calculators and generators for everyday Linux admin work.Scripts5 pagesShort, readable shell scripts for recurring sysadmin tasks.Distros8 pagesQuick facts, support dates and day-to-day commands for each major distribution.Software4 pagesInstall and troubleshoot popular open source applications on any distribution.
How this site works
Every page answers one problem. Error pages start with the exact message you see, explain what causes it in a sentence or two, and give the fix first — background comes after. Commands are written for the current releases (Ubuntu 26.04 LTS, Debian 13, Fedora 44, Arch, Linux Mint 22.3) and each page shows the date it was last checked.
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