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1. Programming
i'm experimenting fork function and i found this code
#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <wait.h>
#include <fcntl.h>
#include <unistd.h>
int main(void)
{
int fd;
pid_t p;
p = fork();
fork();
if (p>0) { fork();}
fork();
fork();... (6 Replies)
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Hello everybody.I want to make clear that i am not going to ask from anybody to build my asignement but i have a big problem. I can't seem to find anywhere ONE good example on C about what i am trying to do:wall:.I think it is simple. All i ask is one example, even a link is fine.
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hi all,
We are trying to run a process in the background and in the process we call fork ;and wait for the child process to finish .We find that the died = wait(&status); happens after 10 seconds randomly and sometimes completes in time (within 1 sec)
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hi all,
We are trying to run a process in the background and in the process we call fork ;and wait for the child process to finish .We find that the died = wait(&status); happens after 10 seconds randomly and sometimes completes in time (within 1 sec)
This behavior is seen only when the... (0 Replies)
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Hi..
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10. Programming
When executing this simple program:
#include <unistd.h>
void main()
{
int f;
printf("\n Parent procces ID=%d\n",getpid());
f=fork();
if(f==0)
{
printf("\n Child process ID=%d father=%d\n",getpid(),getppid());
}
... (2 Replies)
Discussion started by: bb666
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NSENTER(1) User Commands NSENTER(1)
NAME
nsenter - run program with namespaces of other processes
SYNOPSIS
nsenter [options] [program [arguments]]
DESCRIPTION
Enters the namespaces of one or more other processes and then executes the specified program. If program is not given, then ``${SHELL}'' is
run (default: /bin/sh).
Enterable namespaces are:
mount namespace
Mounting and unmounting filesystems will not affect the rest of the system, except for filesystems which are explicitly marked as
shared (with mount --make-shared; see /proc/self/mountinfo for the shared flag). For further details, see mount_namespaces(7) and
the discussion of the CLONE_NEWNS flag in clone(2).
UTS namespace
Setting hostname or domainname will not affect the rest of the system. For further details, see namespaces(7) and the discussion of
the CLONE_NEWUTS flag in clone(2).
IPC namespace
The process will have an independent namespace for POSIX message queues as well as System V message queues, semaphore sets and
shared memory segments. For further details, see namespaces(7) and the discussion of the CLONE_NEWIPC flag in clone(2).
network namespace
The process will have independent IPv4 and IPv6 stacks, IP routing tables, firewall rules, the /proc/net and /sys/class/net direc-
tory trees, sockets, etc. For further details, see namespaces(7) and the discussion of the CLONE_NEWNET flag in clone(2).
PID namespace
Children will have a set of PID to process mappings separate from the nsenter process For further details, see pid_namespaces(7) and
the discussion of the CLONE_NEWPID flag in nsenter will fork by default if changing the PID namespace, so that the new program and
its children share the same PID namespace and are visible to each other. If --no-fork is used, the new program will be exec'ed
without forking.
user namespace
The process will have a distinct set of UIDs, GIDs and capabilities. For further details, see user_namespaces(7) and the discussion
of the CLONE_NEWUSER flag in clone(2).
cgroup namespace
The process will have a virtualized view of /proc/self/cgroup, and new cgroup mounts will be rooted at the namespace cgroup root.
For further details, see cgroup_namespaces(7) and the discussion of the CLONE_NEWCGROUP flag in clone(2).
See clone(2) for the exact semantics of the flags.
OPTIONS
Various of the options below that relate to namespaces take an optional file argument. This should be one of the /proc/[pid]/ns/* files
described in namespaces(7).
-a, --all
Enter all namespaces of the target process by the default /proc/[pid]/ns/* namespace paths. The default paths to the target process
namespaces may be overwritten by namespace specific options (e.g. --all --mount=[path]).
The user namespace will be ignored if the same as the caller's current user namespace. It prevents a caller that has dropped capa-
bilities from regaining those capabilities via a call to setns(). See setns(2) for more details.
-t, --target pid
Specify a target process to get contexts from. The paths to the contexts specified by pid are:
/proc/pid/ns/mnt the mount namespace
/proc/pid/ns/uts the UTS namespace
/proc/pid/ns/ipc the IPC namespace
/proc/pid/ns/net the network namespace
/proc/pid/ns/pid the PID namespace
/proc/pid/ns/user the user namespace
/proc/pid/ns/cgroup the cgroup namespace
/proc/pid/root the root directory
/proc/pid/cwd the working directory respectively
-m, --mount[=file]
Enter the mount namespace. If no file is specified, enter the mount namespace of the target process. If file is specified, enter
the mount namespace specified by file.
-u, --uts[=file]
Enter the UTS namespace. If no file is specified, enter the UTS namespace of the target process. If file is specified, enter the
UTS namespace specified by file.
-i, --ipc[=file]
Enter the IPC namespace. If no file is specified, enter the IPC namespace of the target process. If file is specified, enter the
IPC namespace specified by file.
-n, --net[=file]
Enter the network namespace. If no file is specified, enter the network namespace of the target process. If file is specified,
enter the network namespace specified by file.
-p, --pid[=file]
Enter the PID namespace. If no file is specified, enter the PID namespace of the target process. If file is specified, enter the
PID namespace specified by file.
-U, --user[=file]
Enter the user namespace. If no file is specified, enter the user namespace of the target process. If file is specified, enter the
user namespace specified by file. See also the --setuid and --setgid options.
-C, --cgroup[=file]
Enter the cgroup namespace. If no file is specified, enter the cgroup namespace of the target process. If file is specified, enter
the cgroup namespace specified by file.
-G, --setgid gid
Set the group ID which will be used in the entered namespace and drop supplementary groups. nsenter(1) always sets GID for user
namespaces, the default is 0.
-S, --setuid uid
Set the user ID which will be used in the entered namespace. nsenter(1) always sets UID for user namespaces, the default is 0.
--preserve-credentials
Don't modify UID and GID when enter user namespace. The default is to drops supplementary groups and sets GID and UID to 0.
-r, --root[=directory]
Set the root directory. If no directory is specified, set the root directory to the root directory of the target process. If
directory is specified, set the root directory to the specified directory.
-w, --wd[=directory]
Set the working directory. If no directory is specified, set the working directory to the working directory of the target process.
If directory is specified, set the working directory to the specified directory.
-F, --no-fork
Do not fork before exec'ing the specified program. By default, when entering a PID namespace, nsenter calls fork before calling
exec so that any children will also be in the newly entered PID namespace.
-Z, --follow-context
Set the SELinux security context used for executing a new process according to already running process specified by --target PID.
(The util-linux has to be compiled with SELinux support otherwise the option is unavailable.)
-V, --version
Display version information and exit.
-h, --help
Display help text and exit.
SEE ALSO
clone(2), setns(2), namespaces(7)
AUTHORS
Eric Biederman <biederm@xmission.com>
Karel Zak <kzak@redhat.com>
AVAILABILITY
The nsenter command is part of the util-linux package and is available from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils
/util-linux/>.
util-linux June 2013 NSENTER(1)