Man pages › Compared with Linux and the BSDs

`chmod(1)` on Solnix vs Linux and the BSDs

On Solnix, chmod is the illumos /usr/bin/chmod. Its synopsis has only -f, -R and -@. It has no -h, -H, -L, -P or -v, so scripts that use those flags on Linux or the BSDs will fail. It also edits ACLs and system attributes.

The manual pages

Solnix: chmod(1) from pkgs.solnix.illumos-world-man · illumos.org
Linux: chmod(1) coreutils-full-9.11
FreeBSD: chmod(1) 15.1-RELEASE
OpenBSD: chmod(1) 8.0
NetBSD: chmod(1) 11.0
Standard: POSIX.1-2024 (IEEE Std 1003.1-2024), chmod

What Solnix runs

A default Solnix system runs the illumos chmod at /usr/bin/chmod. No other variants are shipped. It is not GNU chmod, so GNU-only options such as --reference, -c and --preserve-root are not in the Solnix page.

Differences

Compared with	Topic	What differs
all four	symlink options `-h`, `-H`, `-L`, `-P`	The Solnix synopsis is chmod [`-fR`] and lists none of `-h`, `-H`, `-L` or `-P`. Linux and all three BSDs document them. The Solnix page does not say how `-R` treats symbolic links. Source: Solnix chmod(1) SYNOPSIS; Linux chmod(1) -H, -L, -P, -h; FreeBSD chmod(1) -H, -L, -P, -h; OpenBSD chmod(1) -H, -L, -P, -h; NetBSD chmod(1) -H, -L, -P, -h
Linux, FreeBSD	`-v` verbose	Solnix chmod has no `-v`. Linux has `-v` and `-c` (report only changes). FreeBSD has `-v`, and repeating it prints old and new modes. FreeBSD marks `-v` as non-standard and not recommended in scripts. Source: Solnix chmod(1) SYNOPSIS; Linux chmod(1) -v, -c; FreeBSD chmod(1) -v, COMPATIBILITY
Linux, NetBSD	`--reference`	Solnix has no `--reference` to copy the mode from another file. Linux and NetBSD both have `--reference=rfile`. FreeBSD and OpenBSD do not list it. Source: Solnix chmod(1) SYNOPSIS; Linux chmod(1) --reference; NetBSD chmod(1) SYNOPSIS, --reference
all four	ACLs and system attributes	Solnix chmod also modifies ACLs (acl_operation) and boolean read-write system attributes through `-@` named_attribute. The Linux and BSD chmod pages describe only mode bits. FreeBSD's SEE ALSO points to setfacl(1) and chflags(1) instead. Source: Solnix chmod(1) SYNOPSIS, DESCRIPTION; Linux chmod(1) DESCRIPTION; FreeBSD chmod(1) SEE ALSO; OpenBSD chmod(1) SEE ALSO; NetBSD chmod(1) SEE ALSO
all four	setgid on directories	On Solnix, the set-group-ID bit of a directory cannot be set or cleared in absolute mode. You must use symbolic g+s or g-s. The other pages document no such restriction on absolute modes. Source: Solnix chmod(1) Absolute Mode; Linux chmod(1) numeric mode; OpenBSD chmod(1) Absolute modes
all four	mandatory locking (l)	Solnix has an l permission letter for mandatory locking. In absolute mode, 20#0 enables locking when # is 6, 4, 2 or 0. Setting g+s together with +l is an error. The other pages list no l and give 2000 as set-group-ID only. Source: Solnix chmod(1) Absolute Mode (20#0), Symbolic Mode permission l; Linux chmod(1) rwxXst; OpenBSD chmod(1) perm symbols and 2000
all four	sticky bit on non-directories	On Solnix, only the super-user can set the sticky bit on a non-directory file. The Linux and BSD pages in the bundle do not state this restriction. Source: Solnix chmod(1) Symbolic Mode (sticky bit restriction); Linux chmod(1); FreeBSD chmod(1); OpenBSD chmod(1); NetBSD chmod(1)
Linux	recursive symlink default	GNU chmod documents `-H` as the default for `-R` and ignores symlinks met during traversal. The Solnix page, as shown in the bundle, gives no `-H`, `-L` or `-P` and states no symlink behaviour for `-R`. Source: Linux chmod(1) OPTIONS (-H is the default), DESCRIPTION; Solnix chmod(1) SYNOPSIS
FreeBSD, OpenBSD, NetBSD	BSD default is `-P`	FreeBSD and NetBSD default to `-P` under `-R`. OpenBSD follows no symlinks when none of `-H`, `-L`, `-P` is given. The Solnix page does not document these options. Source: FreeBSD chmod(1) -P; NetBSD chmod(1) DESCRIPTION; OpenBSD chmod(1) DESCRIPTION; Solnix chmod(1) SYNOPSIS
OpenBSD	`-f` and `-h` with `-R`	OpenBSD chmod has no `-f`; its synopsis is [`-h`] [`-R` [`-H` \| `-L` \| `-P`]]. Solnix, Linux, FreeBSD and NetBSD accept `-f`. On OpenBSD, `-h` and `-R` are mutually exclusive. Source: OpenBSD chmod(1) SYNOPSIS, -h; Solnix chmod(1) SYNOPSIS; FreeBSD chmod(1) -f; NetBSD chmod(1) -f
FreeBSD, NetBSD	`-f` and exit status	FreeBSD and NetBSD `-f` suppresses the diagnostic and also stops chmod from reflecting the failure in the exit status. Linux describes `-f` only as suppressing most error messages. The bundle's Solnix text does not describe `-f`. Source: FreeBSD chmod(1) -f; NetBSD chmod(1) -f; Linux chmod(1) -f
NetBSD	`-d`	NetBSD `-d` skips files whose mode is already as requested. Solnix has no `-d`. Source: NetBSD chmod(1) -d; Solnix chmod(1) SYNOPSIS

Standards

POSIX: chmod is a POSIX.1-2024 utility.
FreeBSD: chmod is expected to be IEEE Std 1003.2 (“POSIX.2”) compatible, except for the perm symbol “t”, which is not in that standard. -v is non-standard.
OpenBSD: chmod is compliant with the specification. The flags [-HhLP] are extensions to it. The “t” perm symbol is marked as an X/Open System Interfaces option.
NetBSD: chmod is expected to be IEEE Std 1003.2-1992 (“POSIX.2”) compatible, except for the perm symbol “t”.

Writing portable scripts

Use only -R and -f with octal or symbolic modes in portable scripts. Avoid -h, -H, -L, -P, -v, -c, -d and --reference, which are missing on at least one system. OpenBSD also lacks -f.
To set setgid on a directory portably, use symbolic g+s rather than an octal mode. Solnix does not allow setting it in absolute mode.

Every difference here is taken from the manual pages linked above: Solnix's published page, Linux (man-pages and the GNU and util-linux manuals), FreeBSD, OpenBSD and NetBSD. Each row names its source. Where a manual is silent, this page is too. Compiled 2026-10-26. Found a mistake? Mail hackers@lists.solnix.io.