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--- quickreference:unix [2019/01/29 01:18] – external edit 127.0.0.1
+++ quickreference:unix [2020/01/18 19:25] – rodolico
@@ Line 2: / Line 2: @@
 This is just a location where I store various commands I found handy for Unix.
+===== Systems Administration =====
+==== Grab Data via SSH ====
+I needed to grab the output from dmidecode for a bunch of machines. This would have been a good place for something like puppet, but we don't have it fully deployed. However, I have ssh access to most of the machines, so I was trying to figure out how to do it. I wanted the resulting filename to be `hostname -f`.dmidecode, ie the full hostname of the server with .dmidecode at the end. In the following, HOSTNAME is something that ssh can get to.
+<code bash>
+ssh HOSTNAME 'hostname -f ; sudo -S dmidecode' >aaee && FNAM=$(head -1 aaee) ; sed '1d' aaee > $FNAM.dmidecode
+</code>
+Dave came up with most of this, then I modified it for my use. Basically, he is returning the hostname and the output of dmidecode to a local temp file named aaee. If that works, then grab the first line into variable FNAM. Then send everything but the first line to the filename $FNAM.dmidecode.
+Note, since dmidecode requires root privileges, I had to use sudo to get it to work. sudo wants a terminal unless you pass  the -S parameter, in which case it prints the prompt on STDERR and waits for input. That input is not blanked, so it is visible on your monitor.
+===== Disk Management =====
+==== Create Swap file ====
+I generally prefer a swap //file// as opposed to a swap //partition//. While swap partitions can be more efficient, swap files are easier to manage (grow/shrink).
+<code bash>
+fallocate -l 1G /swapfile
+# if no fallocate on your system, use the following
+# dd if=/dev/zero of=/swapfile bs=1024 count=1048576
+chmod 600 /swapfile
+# use "force" to use the entire "device"
+mkswap -f /swapfile
+# save, then modify fstab
+mv /etc/fstab /etc/fstab.save
+echo '/swapfile swap swap defaults 0 0' >> /etc/fstab
+# turn on swap for everything in fstab
+swapon -a
+# display the result
+swapon --show
+</code>
 ===== Shell (mainly BASH) =====
@@ Line 152: / Line 188: @@
 ===== References =====
   * https://stackoverflow.com/questions/2419566/best-way-to-use-multiple-ssh-private-keys-on-one-client#2419609
+  * https://linuxize.com/post/how-to-add-swap-space-on-debian-9/