title: how to increase virtual memory for each one on linux ?(command line)
body: <p>I just allocate some virtual memory for each account, </p>
  
  <pre><code> pi@duckpi01 /etc $ ulimit -v 100
  pi@duckpi01 /etc $ ulimit -v 200
  -bash: ulimit: virtual memory: cannot modify limit: Operation not permitted
  pi@duckpi01 /etc $ ulimit -v 99
  pi@duckpi01 /etc $ ulimit -v 101
  -bash: ulimit: virtual memory: cannot modify limit: Operation not permitted
  pi@duckpi01 /etc $ ulimit -v 100
  -bash: ulimit: virtual memory: cannot modify limit: Operation not permitted
  pi@duckpi01 /etc $ ulimit -v 200
  -bash: ulimit: virtual memory: cannot modify limit: Operation not permitted
  pi@duckpi01 /etc $ cd security
  pi@duckpi01 /etc/security $ vi limits.conf
  Segmentation fault
  pi@duckpi01 /etc/security $ sudo ulimit -v 200
  Segmentation fault
  </code></pre>
  
  <p>But now I cannot use <code>ulimit</code> to allocate memory more than 99. Apparently, 99kbytes is not enough for me to do anything. I use <code>sudo</code>, but it does't work. How could I do to fix this problem?</p>
  
  <p>This doesn't work :</p>
  
  <pre><code>pi@duckpi01 /etc/security $ sudo mount -t tmpfs -o size=2048M tmpfs /media/nameme/
  Segmentation fault
  pi@duckpi01 /etc/security $ sudo mount -t tmpfs -o size=500M tmpfs /media/nameme/
  Segmentation fault
  </code></pre>
  
  <p>This doesn't work,too:</p>
  
  <pre><code>pi@duckpi01 /etc/security $ sudo ulimit -v unlimited
  Segmentation fault
  pi@duckpi01 ~ $ sudo su
  Segmentation fault
  pi@duckpi01 ~ $ mkdir -p /media/nameme
  Segmentation fault
  pi@duckpi01 ~ $ free -m
  Segmentation fault
  pi@duckpi01 ~ $ sudo ulimit -v
  Segmentation fault
  pi@duckpi01 ~ $ ulimit -v
  99
  pi@duckpi01 ~ $ su -u root
  Segmentation fault
  </code></pre>
  
  <p>Doesn't work:</p>
  
  <pre><code>pi@duckpi01 ~ $ ulimit -c unlimited
  pi@duckpi01 ~ $ ulimit -v
  99
  pi@duckpi01 ~ $ ulimit -v 10000
  -bash: ulimit: virtual memory: cannot modify limit: Operation not permitted
  pi@duckpi01 ~ $ ls
  Segmentation fault
  </code></pre>