Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am doing a project in which I need to mount 100+ loop devices and merge it into AUFS mountpoint As an observation, for sequentially mounting 90 loop devices, it takes 25 seconds.

I am looking for a solution which will minimize time by mounting loop devices in parallel

share|improve this question
So what is your current code for this? – Nils Aug 9 '13 at 10:27
up vote 5 down vote accepted

I think this is obvious, but

typeset -i M=1
while [ $M -le 102 ]
    mount mysourcedevice$M targetdir$M &
    let M++

Should do the job. The wait will wait until all sub-processess are finished, before executing the next command.

share|improve this answer
If I have to add "wait" at the end of for loop then there is no point calling mount command in background – SHW Aug 9 '13 at 12:28
@SHW The wait is outside/after the loop. The loop starts all mounts in paralell. I assume you want to do something after the parallel mounts have finished. – Nils Aug 9 '13 at 21:18
Yes...After parallel mounting,I am starting X. and to start X, all loop devices NEED to be mounted beforehand – SHW Aug 10 '13 at 7:30
@SHW This code mounts them in parallel; you can do your other stuff after the wait. There isn't anything else to be done. While a C version may be slightly faster still (lacks the overhead of calling mount command a hundred times) it's usually not practical. – frostschutz Aug 12 '13 at 11:04
agree with @frostschutz, try the C version only if performance is an issue. – Alex Aug 13 '13 at 11:59

Maybe a threaded version could be a bit faster, you've to adjust the mount() parameters yourself.

#include <stdio.h>
#include <pthread.h>
#include <sys/mount.h>
#include <string.h>
#include <errno.h>

#define DEVS 100

static void *mountt(void *d)
    int i = (int)d;
    char loop[48], mp[48];

    snprintf(loop, 47, "/dev/loop%d", i);
    snprintf(mp, 47, "/mnt/%d", i);

    if (mount(loop, mp, "ext2", MS_MGC_VAL | MS_RDONLY | MS_NOSUID, "") < 0)
        fprintf(stderr, "mount[%d]: failed: %s\n", i, strerror(errno));

    return NULL;

int main(int argc, char **argv)
    int i;
    pthread_t tt[DEVS];

    for (i=0; i<DEVS; i++) {
        if (pthread_create( &tt[i], NULL, mountt, (void*)i) != 0)
            fprintf(stderr, "thread create[%d] failed: %s\n", i, strerror(errno));

    for (i=0; i<DEVS; i++)
        pthread_join(tt[i], NULL);

    return 0;

gcc -O2 -Wall -o mountt mountt.c -lpthread

share|improve this answer
Thnx. I Will check first and then update you – SHW Aug 12 '13 at 9:24

Using GNU Parallel it looks like this:

seq 100 | parallel -j0 mount device{} dir{}

If you have a list of dirs:

parallel -j0 mount device{#} {} ::: dirs*

If you have a list of devices:

parallel -j0 'mkdir -p dir{#}; mount {} dir{#}' ::: device*

GNU Parallel is a general parallelizer and makes is easy to run jobs in parallel on the same machine or on multiple machines you have ssh access to. It can often replace a for loop.

If you have 32 different jobs you want to run on 4 CPUs, a straight forward way to parallelize is to run 8 jobs on each CPU:

Simple scheduling

GNU Parallel instead spawns a new process when one finishes - keeping the CPUs active and thus saving time:

GNU Parallel scheduling


If GNU Parallel is not packaged for your distribution, you can do a personal installation, which does not require root access. It can be done in 10 seconds by doing this:

(wget -O - pi.dk/3 || curl pi.dk/3/ || fetch -o - http://pi.dk/3) | bash

For other installation options see http://git.savannah.gnu.org/cgit/parallel.git/tree/README

Learn more

See more examples: http://www.gnu.org/software/parallel/man.html

Watch the intro videos: https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1

Walk through the tutorial: http://www.gnu.org/software/parallel/parallel_tutorial.html

Sign up for the email list to get support: https://lists.gnu.org/mailman/listinfo/parallel

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.