[solved] Setting up a "persistent" ramdisk with systemd

Question

I have been doing much thinking in terms of using a ramdisk (tmpfs) to mitigate, or rather postpone SSD write limit issues as well as to enhance system performance. After following the steps described in the Ramdisk wiki page to no avail, I realized I have a systemd setup. I have also found another topic describing how to "hack" init scripts into the systemd build but I am not sure this is the "right" (or most elegant) way. Essentially I would like to move/copy several folders to a ramdisk and have its contents written back to disk after system suspend/shutdown. Just general guidelines would suffice!
(1) How should I go about setting up a "persistent" ramdisk with systemd? How would I setup "before" and "after" hooks?
(2) From what I have gathered so far, it appears that for the above, using rsync rather than cp would be a more efficient way to write ramdisk contents to disk. Is this true?
(3) The example described in the Ramdisk wiki page loads pacman cache and lib into a ramdisk. How about completely putting /var to a ramdisk?
(4) Will doing what I have described above (including /var) possibly leave my system in an inconsistent state?
I am trying to get this running on a computer with 8 GB of RAM on which memory usage rarely goes above 2 GB. I am not too worried about power failures as what I intend to put on the ramdisk is not mission critical (with the possible exception of /var).
I apologize in advance if I posted my concerns in the wrong subforum as I am both a Linux rookie and an Arch noob; I have also tried using the search function but I may have formulated my query improperly (the answers seemed irrelevant!) Thanks in advance for your time and please let me know if I have omitted important details.
Last edited by ndejay (2012-10-31 13:50:02)

Answer 1

#create 'ramdisksave' directory using terminal
mkdir /home/ramdisksave
#edit grub config or custom_40. This allocates max ram for ramdisks
kernel /vmlinuz ramdisk_size=2048000
#edit rc.local add these lines to create & mount ramdisk at boot
mke2fs -t ext2 /dev/ram1 2048000
mount /dev/ram1 /home/ramdisksave
#copies 'ramdisksave' contents to ramdisk save as *.sh make exe!
cp -a /home/ramdisksave/.  /mnt/ram1
#saves ramdisk contents to ramdisksave folder save as *.sh make exe!
cp -a /mnt/ram1/.  /home/ramdisksave/
#deletes ramdisk contents save as *.sh make exe!
cd /mnt && rm -rf ram1/*
#deletes ramdisksave contents save as *.sh make exe! DANGEROUS!!
cd /home && rm -rf ramdisksave/*
for safety better to create ramdisksave on another partition.  Scripts can be crontabbed, can add tar compression options to save space, use rsync to copy only  new etc etc.......script lines can be added to r.sysinit for startup and rc.shutdown for load and save at startup and shutdown.
Last edited by st.emsee (2013-06-22 11:23:44)