quickreference:unix
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| quickreference:unix [2023/10/08 14:53] – rodolico | quickreference:unix [2025/02/05 00:12] (current) – [Shell (mainly BASH)] rodolico | ||
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| ===== Systems Administration ===== | ===== Systems Administration ===== | ||
| + | ==== Partitioning large drives ==== | ||
| + | |||
| + | Drives greater than 2 Terabytes are not handled well by the standard //fdisk// application, | ||
| + | |||
| + | This assumes we have a drive, sdg, that we want to set up with gpt and create one partition on. That partition will set up on optimal sector boundries, and use all of the space available. | ||
| + | |||
| + | <code bash> | ||
| + | # remove all old file system information. Not necessary, but I do it just because I can | ||
| + | wipefs -a /dev/sdg | ||
| + | # make this a gpt disk. Will wipe out any other partitioning scheme | ||
| + | parted /dev/sdg mklabel gpt | ||
| + | # make a new partition on optimal sector boundries. This is a primary partition, and starts | ||
| + | # at the beginning of the disk (0%) and goes to the end of the disk (100%) | ||
| + | # I put that in quotes as, from what I've read, the percent symbol does not work well | ||
| + | # within the bash command line | ||
| + | # note, we are not telling it what file system to use, so it defaults to Linux | ||
| + | parted -a optimal /dev/sdg mkpart primary ' | ||
| + | # display the information on the disk | ||
| + | parted /dev/sdg print | ||
| + | # format as ext4, no reserved space, and a disk label marked ' | ||
| + | mkfs.ext4 -m0 -Lbackup /dev/sdg | ||
| + | |||
| + | </ | ||
| ==== Rapidly wipe multiple hard drives ==== | ==== Rapidly wipe multiple hard drives ==== | ||
| Line 13: | Line 36: | ||
| # for truly not sensitive information, | # for truly not sensitive information, | ||
| - | for drive in a b c d e f g ; do wipefs -a / | + | for drive in a b c d e f g |
| + | do | ||
| + | wipefs -a / | ||
| + | done | ||
| # but, to really remove in a way that takes tons of effort to recover, do this also | # but, to really remove in a way that takes tons of effort to recover, do this also | ||
| - | for drive in a b c d e f g ; do echo Cleaning sd%drive | + | for drive in a b c |
| + | do | ||
| + | echo Cleaning sd%drive | ||
| + | dd if=/ | ||
| + | done | ||
| </ | </ | ||
| - | I then realized | + | I had 7 drives to wipe, and this takes about 5 hours per drive, so a total of 35 hours. |
| <code bash wipedrives2.sh> | <code bash wipedrives2.sh> | ||
| #! / | #! / | ||
| - | for drive in a b c d e f g ; do screen dd if=/ | + | for drive in a b c d e f g h |
| + | do | ||
| + | screen | ||
| + | done | ||
| </ | </ | ||
| - | Note: I have not done the parallel one yet. I'm waiting | + | Basically, we're using a bash for loop to grab all the drive names (I just used the last letter), running screen and immediately detaching the new process after telling it to run //bash -c// and the command after it in quotes |
| - | + | ||
| - | Haven' | + | |
| **Warning**: | **Warning**: | ||
| Line 40: | Line 71: | ||
| </ | </ | ||
| - | |||
| - | |||
| - | |||
| - | ==== Check SSL Cert Expiration Date ==== | ||
| - | |||
| - | Ever wondered when your SMTP SSL Certificates are up for renewal? A quick and dirty way of doing it from the command line was shown at [https:// | ||
| - | |||
| - | Note: the discussion covered other things, and is well worth a 5 minute read. | ||
| - | |||
| - | <code bash> | ||
| - | printf ' | ||
| - | openssl s_client -connect smtp.example.com: | ||
| - | openssl x509 -dates -noout | ||
| - | </ | ||
| ==== Rename Server ==== | ==== Rename Server ==== | ||
| Line 67: | Line 84: | ||
| <code bash> | <code bash> | ||
| # change the host name, and the postfix name if that is installed | # change the host name, and the postfix name if that is installed | ||
| - | sed -i.old ' | + | sed -i.old ' |
| + | / | ||
| + | / | ||
| + | / | ||
| + | / | ||
| + | / | ||
| + | / | ||
| / | / | ||
| # update the aliases, if they exist | # update the aliases, if they exist | ||
| Line 214: | Line 237: | ||
| ===== Shell (mainly BASH) ===== | ===== Shell (mainly BASH) ===== | ||
| + | ==== Here Documents ==== | ||
| + | |||
| + | Most unix users are familiar with echo' | ||
| + | |||
| + | A **here document** is a way of having multiple lines processed at one time. In many cases, you can have similar functionality using quotes, but here documents are more robust. | ||
| + | |||
| + | For example, a simple test of a newly built mail system might include creating a file with all of the headers necessary, then passing that to // | ||
| + | |||
| + | <code bash> | ||
| + | sendmail user@example.com << EOF | ||
| + | To: user@example.com | ||
| + | from: root@example.org | ||
| + | Subject: test | ||
| + | |||
| + | This is a test | ||
| + | EOF | ||
| + | </ | ||
| + | |||
| + | The entire block above is one command. Here is the breakdown. | ||
| + | |||
| + | - //sendmail user@example.com// | ||
| + | - //<<// | ||
| + | - //EOF// is the tag which will mark the end of the text for the here document | ||
| + | - Everything up to the EOF is the actual string to be passed to sendmail | ||
| + | - //EOF// at the end marks the end of the here document. **Note**: there must be no leading or trailing whitespace. The tag must be exactly as entered after the << (case sensitive), and must be the only thing on the final line. | ||
| + | |||
| + | This only touches the surface of here documents. See [[https:// | ||
| ==== Find files within date range containing text ==== | ==== Find files within date range containing text ==== | ||
| Line 387: | Line 437: | ||
| * https:// | * https:// | ||
| * https:// | * https:// | ||
| + | * https:// | ||
| + | * https:// | ||
quickreference/unix.1696794786.txt.gz · Last modified: 2023/10/08 14:53 by rodolico