util-linux

util-linux is a collection of system utilities maintained as an independent upstream project. It supplies interfaces for block devices, mounts, terminals, sessions, namespaces, resource control, and data formatting. Distributions can split utilities into separate packages, so installed commands depend on packaging policy.

Operational Boundaries #

Commands that modify partitions, mounts, swap, device state, process credentials, or namespaces require suitable privileges. Inspect state before changing it, identify devices through stable attributes such as UUID or /dev/disk/by-id, and confirm a target is not mounted or in active use.

The project spans several kernel interfaces:

• lsblk, blkid, blockdev, fdisk, and wipefs inspect sysfs, device nodes, ioctls, and on-disk signatures;
• mount, umount, findmnt, and fsfreeze operate on the VFS mount API and /proc/self/mountinfo;
• unshare, nsenter, setpriv, prlimit, taskset, and chrt configure process namespaces, credentials, resource limits, affinity, and schedulers;
• agetty, script, setterm, and wall operate on terminals and login records.

The exact command set depends on the util-linux build configuration and distribution packaging. Use command --help, the command’s man page, and the distribution’s package metadata or an individual command’s --version output before depending on a recent option.

Command Reference #

Common Workflows #

lsblk --fs, blkid, findmnt, and mountpoint inspect storage without changing it:

lsblk --json --output NAME,PATH,SIZE,FSTYPE,UUID,MOUNTPOINTS
findmnt --json --output SOURCE,TARGET,FSTYPE,OPTIONS
blkid --probe --usages filesystem /dev/disk/by-id/example

Specify columns in scripts because default output changes as util-linux adds information. Prefer --json, --pairs, or --raw where supported, and set LC_ALL=C if parsing human-readable diagnostics. Never parse the aligned default table as a stable interface.

fdisk, cfdisk, and sfdisk modify partition tables. Save the current layout with sfdisk --dump and verify the device by size, model, serial, and stable path before writing. partx asks the kernel to add or remove partition mappings after an intended table change; it does not edit the on-disk table. mkswap prepares a swap area, then swapon enables it and swapoff disables it.

unshare, nsenter, setpriv, runuser, setarch, and taskset affect execution context. A namespace or affinity change does not grant permissions; capabilities, user mappings, and cgroup policy still determine what the process can do.

unshare --user --map-root-user --mount-proc sh
nsenter --target "$pid" --mount --uts --ipc --net --pid
script --log-out session.typescript --log-timing session.timing

nsenter joins the selected namespaces of an existing process and therefore requires permission to inspect and enter them. unshare availability for unprivileged user namespaces is controlled by the kernel and local security policy.

script, scriptreplay, and scriptlive can capture terminal sessions. Recorded input may contain credentials or other secrets, so files require access controls appropriate to their contents.