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braid idle

Check if the pool has any active operations. Designed for autosuspend integration.

When to use it

• As an autosuspend check to prevent the system from sleeping during a scrub or any btrfs exclusive operation (balance, device add, device remove, device replace, resize, swap activate)
• In scripts that need to wait for the pool to be idle before proceeding

Basic example

sudo braid idle

Output when the pool is mounted and idle:

idle: pool is idle

Output when the pool is not mounted (still exit 0 – nothing to protect):

idle: pool is offline

Exit codes

The busy reason is printed to stdout:

busy: scrub running (45%)
busy: balance running
busy: balance paused
busy: device add in progress
busy: device remove in progress
busy: device replace in progress
busy: resize in progress
busy: swap activate in progress
busy: unknown (<probe>: <error>)

Only the scrub line carries a percentage. The named btrfs operation states come from scanning /sys/fs/btrfs/*/exclusive_operation, which reports the active operation but not its progress.

busy: unknown (<probe>: <error>) is printed when a probe failed. The probe label is mountinfo for /proc/self/mountinfo, sysfs for /sys/fs/btrfs/*/exclusive_operation, or scrub for btrfs scrub status command/parser failures. The error text preserves the underlying diagnostic.

When the pool is offline (not mounted), exit code is 0 – there is nothing to protect, so suspend is safe.

braid idle must run as root. A non-root invocation exits 1 with error: braid must be run as root on stderr before config loading or any probe runs, with no stdout output. The streams disambiguate this from the documented exits above: exit 0 prints idle: on stdout, busy/probe-failure exit 1 prints busy: on stdout, and config-load exit 2 emits a config-error diagnostic.

Autosuspend integration

braid idle is the activity check behind braid’s auto-suspend. You don’t write this check by hand: set braid.autoSuspend.enable = true and braid’s NixOS module generates the autosuspend services.autosuspend ExternalCommand check (BraidPool) for you. The generated command – bash -c '! timeout -k 2 10 braid idle', with fully qualified /nix/store paths for bash, timeout, and braid – handles the exit-code inversion autosuspend expects and a fail-closed inner timeout. Don’t reproduce it by hand: autosuspend runs the check outside braid’s wrapper, so bare braid/timeout are not on its PATH.

See the power management guide for setup, and ADR 016: Auto-Suspend for the exit-inversion table, the qualified-path requirement, and why timeout must sit inside the !-inverted command.

What happens under the hood

1. Checks if the pool is mounted (via /proc/self/mountinfo)
2. If not mounted: returns idle (exit 0)
3. Reads /sys/fs/btrfs/*/exclusive_operation for any active exclusive operation on any btrfs filesystem: balance, balance paused, device add, device remove, device replace, resize, swap activate
4. If sysfs reports a busy operation or the sysfs probe fails, returns immediately before probing scrub
5. Probes scrub status via btrfs scrub status against the configured pool mount point, only after the sysfs scan is clean (scrub is not in the kernel exclusive-operation set, so sysfs cannot detect it)

When the host has more than one btrfs filesystem (e.g. a btrfs root in addition to the pool), an exclusive op on any of them keeps the system awake while the pool is mounted, and the busy: line above may name an op on the non-pool fs. This is intentionally conservative – see ADR 016: Auto-Suspend. Scrub detection is narrower: braid idle only checks for a scrub on the braid pool itself, so a scrub running on a non-pool btrfs (e.g. the btrfs root) is not detected and does not block suspend.

Related commands

• braid status – detailed pool state including operation progress
• braid lock – take the pool offline