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    Creative Commons License
    This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
    PyBlosxom

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    Tue, 09 Jun 2015


    /Admin/commandLine/misc: Send E-mail From the Command Line

    echo "This will go into the body of the mail." | mail -s "Hello world" you@youremail.com
    Or, if you wish to send to a remote SMTP server, install the heirloom-mailx package and:
    export smtp=host:port
    mailx -s "some subject" address@example.com
    some random body text
    ctrl-D

    This also works well in a cron job.

    posted at: 21:57 | path: /Admin/commandLine/misc | permanent link to this entry

    Mon, 29 Jul 2013


    /Admin/commandLine/misc: Fingerprint a Public GPG Key

    This is particularly interesting in the context of RetroShare[1], and the prevention of Man-In-The-Middle (MITM) attacks:

    gpg --with-fingerprint file-containing-public-key.rsc

    Both sides of the key exchange should generate a fingerprint for both keys, and then compare the fingerprints over another communication channel (definitely NOT using RetroShare!).

    [1] http://retroshare.sourceforge.net/

    posted at: 02:42 | path: /Admin/commandLine/misc | permanent link to this entry

    Sun, 21 Jul 2013


    /Admin/commandLine/misc: Resuscitating A Damaged Hard Disk

    So my laptop received a pretty hard knock while being turned on, and a part of the disk was destroyed. Having gotten everything I could off the thing (I did not lose anything important) my thoughts now turn to "can I fix it". It is, after all, a newish 500G disk with a non-trivial price tag. Let's try:

    First put the thing in a USB enclosure, hook it up, and use your favorite partition editor to divide it into several partitions (I chose five 100G partitions). Then start testing the partitions one by one, with a read/write test, ie.:

    e2fsck -k -c -c /dev/sdb1
    dumpe2fs -b /dev/sdb1

    Remove any partitions that have errors. Then install Debian in the ones that are left, using LVM to stitch them all together. Wish me luck....

    posted at: 08:58 | path: /Admin/commandLine/misc | permanent link to this entry

    Tue, 02 Jul 2013


    /Admin/commandLine/misc: Web Page to HTML

    Especially when the page runs off the screen and a screenshot just will not do the job:

    wkhtmltopdf http://blog.langex.net/ /tmp/webpage.pdf

    And really useful for those of us whose primary CV is a web page.

    posted at: 02:07 | path: /Admin/commandLine/misc | permanent link to this entry

    Sat, 08 Jun 2013


    /Admin/commandLine/misc: yum: Use Just One Repo to Fix Broken Dependency

    Recently seen on Amazon AWS' "Linux" distribution: mosh would not install because of a broken dependency on libprotobuf. This was a soluble problem, because an installable version of mosh existed in the epel repo, but yum insisted on installing the most recent version from the AWS repo, even though it was broken. The fix is to restrict yum to consider only packages from epel, and ignore all other repos:

    yum --disablerepo "*" --enablerepo "epel" install protobuf mosh

    posted at: 02:33 | path: /Admin/commandLine/misc | permanent link to this entry

    Wed, 05 Jun 2013


    /Admin/commandLine/misc: Processing Lists

    Suppose, for instance, you want to remove all i386 packages from an amd64 install:

    apt-get remove $(wajig list-installed | grep i386)

    posted at: 10:06 | path: /Admin/commandLine/misc | permanent link to this entry

    Tue, 12 Jun 2012


    /Admin/commandLine/misc: Convert Unix/Linux Time to Human-Readable Time

    This displays the Unix time in seconds:

    $ date +%s

    This converts time in seconds 1190000000 to a readable date/time:

    $ date -d @1190000000

    posted at: 04:00 | path: /Admin/commandLine/misc | permanent link to this entry

    Wed, 07 Sep 2011


    /Admin/commandLine/misc: Logging to the System Log

    This is actually more of a scripting thing, but what is a bash script except a collection of command lines....

    To send a bit of text to /var/log/syslog:

    logger Hello logging world!!

    If you wish the output of a particular line in the script to be logged:

    mysql -V | logger

    will send the MySQL version to syslog. If you wish to also capture errors (STDERR) output, this will do it:

    mysql < /path/to/a/sql/script.sql 2>&1 | logger

    will send both script and error output to syslog.

    posted at: 05:55 | path: /Admin/commandLine/misc | permanent link to this entry

    Tue, 17 May 2011


    /Admin/commandLine/misc: User Group Management

    To find out what groups a user belongs too:

    groups username

    The easiest way to add a group to a user:

    adduser username groupname

    However, this does not work on all Linux distributions (CentOS?). A more general method:

    usermod -a -G groupname username

    posted at: 22:29 | path: /Admin/commandLine/misc | permanent link to this entry

    Fri, 24 Jul 2009


    /Admin/commandLine/misc: Difficulty Unmounting

    When unmounting a partition / device, for example

    umount /media/thumb

    One might encounter a "busy" error, which indicates some process is still using the partition in question. To perhaps find out who / what is using the partition and do something about it:

    lsof | grep '/media/thumb'

    And as a last resort, kill all process accessing the partition:

    fuser -km /media/thumb
    umount /media/thumb

    posted at: 06:07 | path: /Admin/commandLine/misc | permanent link to this entry