NAME Linux::Clone - an interface to the linux clone, unshare, setns, pivot_root and kcmp syscalls SYNOPSIS use Linux::Clone; DESCRIPTION This module exposes the linux clone(2), unshare(2) and some related syscalls to Perl. $retval = unshare $flags The following CLONE_ flag values (without CLONE_ prefix) are supported for unshare, if found, in this release. See the documentation for unshare(2) for more info on what they do: Linux::Clone::FILES Linux::Clone::FS Linux::Clone::NEWNS (in unshare, implies FS) Linux::Clone::VM (in unshare, implies SIGHAND) Linux::Clone::THREAD (in unshare, implies VM, SIGHAND) Linux::Clone::SIGHAND Linux::Clone::SYSVSEM Linux::Clone::NEWUSER (in unshare, implies CLONE_THREAD) Linux::Clone::NEWPID Linux::Clone::NEWUTS Linux::Clone::NEWIPC Linux::Clone::NEWNET Linux::Clone::NEWCGROUP Linux::Clone::NEWTIME Example: unshare the network namespace and prove that by calling ifconfig, showing only the unconfigured lo interface. Linux::Clone::unshare Linux::Clone::NEWNET and "unshare: $!"; Linux::Clone::configure_loopback; system "ifconfig"; Example: unshare the network namespace, initialise the loopback interface, create a veth interface pair, put one interface into the parent processes namespace (use ifconfig -a from another shell), configure the other interface with 192.168.99.2 -> 192.168.99.1 and start a shell. use Linux::Clone; # unshare our network namespace Linux::Clone::unshare Linux::Clone::NEWNET and "unshare: $!"; Linux::Clone::configure_loopback; my $ppid = getppid; system " # create veth pair ip link add name veth_master type veth peer name veth_slave # move veth_master to our parent process' namespace ip link set veth_master netns $ppid # configure the local interface ip link set veth_slave up ip addr add 192.168.99.2/32 dev veth_slave ip route add 192.168.99.1/32 dev veth_slave "; print <<EOF; say hi to your new network namespace, use exit to return. try this from another shell to get networking up: ip link set veth_master up ip addr add 192.168.99.1/32 dev veth_master ip route add 192.168.99.2/32 dev veth_master EOF system "bash"; Example: unshare the filesystem namespace and make a confusing bind mount only visible to the current process. use Linux::Clone; Linux::Clone::unshare Linux::Clone::NEWNS and die "unshare: $!"; # now bind-mount /lib over /etc and ls -l /etc - looks scary system "mount -n --bind /lib /etc"; system "ls -l /etc"; $retval = Linux::Clone::clone $coderef, $stacksize, $flags[, $ptid, $tls, $ctid] Clones a new process as specified via $flags and calls $coderef without any arguments (a closure might help you if you need to pass arguments without global variables). The return value from coderef is returned to the system. The $stacksize specifies how large a stack to allocate for the child. If it is 0, then a default stack size (currently 4MB) will be allocated. There is currently no way to free this area again in the child. $ptid, if specified, will receive the thread id, $tls, if specified, must contain a "struct user_desc" and $ctid is currently totally unsupported and must not be specified. Since this call basically bypasses both perl and your libc (for example, $$ might reflect the parent *or* child pid in the child), you need to be very careful when using this call, which means you should probably have a very good understanding of perl memory management and how fork and clone work. The following flags are supported for clone, in addition to all flags supported by "unshare", above, and a signal number. When in doubt, refer to the clone(2) manual page. Linux::Clone::PTRACE Linux::Clone::VFORK Linux::Clone::SETTLS (not yet implemented) Linux::Clone::PARENT_SETTID (not yet implemented) Linux::Clone::CHILD_SETTID (not yet implemented) Linux::Clone::CHILD_CLEARTID (not yet implemented) Linux::Clone::PIDFD (not yet implemented) Linux::Clone::DETACHED Linux::Clone::UNTRACED Linux::Clone::IO Linux::Clone::CSIGNAL exit signal mask Note that for practical reasons you basically must not use "Linux::Clone::VM" or "Linux::Clone::VFORK", as perl is unlikely to cope with that. This is the glibc clone call, it cannot be used to emulate fork. Example: do a fork-like clone, sharing nothing, slightly confusing perl and your libc, and exit immediately. my $pid = Linux::Clone::clone sub { warn "in child"; 77 }, 0, POSIX::SIGCHLD; Linux::Clone::setns $fh_or_fd[, $nstype] Calls setns(2) on the file descriptor (or file handle) $fh_or_fd. If $nstype is missing, then 0 is used. The argument $nstype can be 0, "Linux::Clone::NEWIPC", "Linux::Clone::NEWNET", "Linux::Clone::NEWUTS", "Linux::Clone::NEWCGROUP", "Linux::Clone::NEWNS", "Linux::Clone::NEWPID" or "Linux::Clone::NEWUSER". Linux::Clone::pivot_root $new_root, $old_root Calls pivot_root(2) - refer to its manpage for details. Linux::Clone::kcmp $pid1, $pid2, $type[, $idx1, $idx2] Calls kcmp(2) - refer to its manpage for details on operations. The following $type constants are available if the kcmp syscall number was available during compilation: "Linux::Clone::KCMP_FILE", "Linux::Clone::KCMP_VM", "Linux::Clone::KCMP_FILES", "Linux::Clone::KCMP_FS", "Linux::Clone::KCMP_SIGHAND", "Linux::Clone::KCMP_IO", "Linux::Clone::KCMP_SYSVSEM" and "Linux::Clone::KCMP_EPOLL_TFD". Linux::Clone::configure_loopback Configures a working loopback interface (basically, does the equivalent of "ifconfig lo up" which automatically adds ipv4/ipv6 addresses and routes), which can be useful to get a network namespace going. Dies on error and returns nothing. "ioctl" symbols The following ioctl symbols are also provided by this module (see ioctl_ns(8)). Linux::Clone::NS_GET_USERNS Linux::Clone::NS_GET_PARENT Linux::Clone::NS_GET_NSTYPE Linux::Clone::NS_OWNER_UID SEE ALSO IO::AIO has some related functions, such as "pidfd_send_signal", and some unrelated functions that might be useful. namspaces(7), cgroup_namespaces(7), pid_namespaces(7), user_namespaces(7), time_namespaces(7), ip-netns(8), switch_root(8), ioctl_ns(2), lsns(8)Q AUTHOR Marc Lehmann <schmorp@schmorp.de> http://home.schmorp.de/