NAME

       enosys - utility to make syscalls fail with ENOSYS

SYNOPSIS

       enosys [--syscall|-s syscall] command

DESCRIPTION

       enosys is a simple command to execute a child process for which certain syscalls fail with errno ENOSYS.

       It can be used to test the behavior of applications in the face of missing syscalls as would happen when
       running on old kernels.

OPTIONS

       -s, --syscall
           Syscall to block with ENOSYS. Can be specified multiple times. An alternative error number or name
           can be specified with a colon.

       -i, --ioctl
           Ioctl to block with ENOTTY. Can be specified multiple times. An alternative error number or name can
           be specified with a colon.

       -l, --list
           List syscalls known to enosys.

       -m, --list-ioctl
           List ioctls known to enosys.

       -d, --dump[=file]
           Dump seccomp bytecode filter to standard output.

           The dump can for example be used by setpriv --seccomp-filter.

       -h, --help
           Display help text and exit.

       -V, --version
           Display version and exit.

EXAMPLES

           # fail syscall "fallocate" with ENOSYS
           enosys -s fallocate ...

           # fail syscall "fallocate" with ENOMEM
           enosys -s fallocate:ENOMEM ...

           # fail syscall "fallocate" with value 12/ENOMEM
           enosys -s fallocate:12 ...

           # fail ioctl FIOCLEX with ENOTTY
           enosys -i FIOCLEX ...

           # fail ioctl FIOCLEX with ENOMEM
           enosys -i FIOCLEX:ENOMEM ...

           # fail ioctl FIOCLEX with value 12/ENOMEM
           enosys -i FIOCLEX:12 ...

EXIT STATUS

       enosys exits with the status code of the executed process. The following values have special meanings:

       1
           internal error

       2
           system does not provide the necessary functionality

AUTHORS

       Thomas Weißschuh <thomas@t-8ch.de>

SEE ALSO

       syscall(2)

REPORTING BUGS

       For bug reports, use the issue tracker <https://github.com/util-linux/util-linux/issues>.

AVAILABILITY

       The enosys command is part of the util-linux package which can be downloaded from Linux Kernel Archive
       <https://www.kernel.org/pub/linux/utils/util-linux/>.

util-linux 2.41                                    2025-02-26                                          ENOSYS(1)