Packages and Binaries

When something behaves unexpectedly, confirm what binary is being executed and where it came from.

Core commands

which <command>
type <command>                # show whether it is a binary, alias, or shell builtin
whereis <command>             # show likely binary and manpage locations
<command> --version
apt list --installed          # list installed packages on Debian-based systems
dnf list installed            # list installed packages on RPM-based systems
rpm -q <package>              # query one RPM package by name
dpkg -l | grep <package>      # search installed Debian packages

What to check

Binary path:

which <command>
readlink -f $(which <command>) # resolve symlinks to the real binary

Package ownership on Debian-based systems:

dpkg -S /path/to/file

Package ownership on RPM-based systems:

rpm -qf /path/to/file

What matters

• Packaged binaries usually live in /usr/bin or /usr/sbin.
• Locally installed tools often land in /usr/local/bin.
• Custom software may live in /opt or a team-owned directory.
• Multiple versions of the same command in PATH cause a lot of confusion.

Common mistake

Do not assume the binary you run interactively is the same one a service uses. Check ExecStart= in the unit file if systemd owns it.