create an emergency swapfile when the existing swap space is getting tight

sudo dd if=/dev/zero of=/swapfile bs=1024 count=1024000;sudo mkswap /swapfile; sudo swapon /swapfile
Create a temporary file that acts as swap space. In this example it's a 1GB file at the root of the file system. This additional capacity is added to the existing swap space.
Sample Output
%free -tom
             total       used       free     shared    buffers     cached
Mem:          1010        997         12          0          1        395
Swap:         2047         43       2003
Total:        3057       1041       2016

%sudo dd if=/dev/zero of=/swapfile bs=1024 count=1024000;sudo mkswap /swapfile; sudo swapon /swapfile

1024000+0 records in
1024000+0 records out
1048576000 bytes (1.0 GB) copied, 48.22 s, 21.7 MB/s
Setting up swapspace version 1, size = 1048571 kB
no label, UUID=1c269910-c4f4-441d-a65c-3cd0ff2a4f31

free -tom
             total       used       free     shared    buffers     cached
Mem:          1010        997         13          0          1        400
Swap:         3047         64       2983
Total:        4057       1061       2996

18
By: dcabanis
2009-05-27 21:10:50

What Others Think

sudo bximage -hd -mode=flat -size=1024 -q /swapfile; sudo mkswap /swapfile; sudo swapon /swapfile As it is much less resource (i.e. cpu and hd) consuming time dd if=/dev/zero of=/swapfile bs=1024 count=1024000 (...) dd if=/dev/zero of=/swapfile bs=1024 count=1024000 0.33s user 7.34s system 34% cpu 22.552 total time bximage -hd -mode=flat -size=1024 -q .swapfile (...) bximage -hd -mode=flat -size=1024 -q /swapfile 0.00s user 0.00s system 58% cpu 0.005 total time /sbin/mkswap /swapfile mkswap: d.img: warning: don't erase bootbits sectors on whole disk. Use -f to force. Setting up swapspace version 1, size = 1048316 KiB no label, UUID=xxxxxxxx /sbin/mkswap /swapfile 0.00s user 0.00s system 0% cpu 0.647 total bximage is part of boche emulator - but is is suitable as we are not interested in any particular content (zero) so we don't mind garbage inside.
MaciejPiechotka · 541 weeks and 3 days ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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