Latest Updates: linux

  • Finding out when (and where from) a user last logged into a Linux/BSD machine

    00:21 on January 2, 2010 | 0 Comments Tweet This! | Digg This!
    Tags: , linux,

    There may be times when you want to find out when and where from a user last logged into a Linux or BSD machine.

    Of course, you could trawl through auth logs, but there is a quicker way by using “lastlog“.

    lastlog is a command which shows you the last login time and also from where (if it was a remote session, it’ll show you the IP/Hostname) a user logged in.

    If you log into the machine and at a terminal run, you’ll get the information:

    droptips@server:~$ lastlog
Username         Port     From             Latest
root                                       **Never logged in**

    (I’ve removed all of my information for security reasons)

    There is a man page available for “lastlog” accessible via:

    droptips@server:~$  man lastlog

    You can also read the Ubuntu 9.10 man page for lastlog here: http://manpages.ubuntu.com/manpages/karmic/man8/lastlog.8.html
    The Wikipedia page is here:  http://en.wikipedia.org/wiki/Lastlog
     

  • Viewing Another Users’ Crontab Entries in Ubuntu, Debian or CentOS

    21:15 on August 11, 2009 | 0 Comments Tweet This! | Digg This!
    Tags: linux,

    There may be occasions where you, as the administrator of a machine, may want to see what cron entries your users have.  Maybe you have slow downs at a particular time every day, and want to see who’s running what.

    All crontab’s, for all users, are stored in /var/spool/cron/crontabs on Debian and Ubuntu, as plain text files.   So, as root, you will be able to cat any of the files in there – they are stored as the username, so:

    /var/spool/cron/crontabs/daz

    … would be a user called “daz” for example.

    In CentOS, the path is slightly different – there is no crontabs directory, so it’s simply:

    /var/spool/cron/

    You can also find out an individual users’ crontab by issuing (as root);

    crontab -l -u username

    This will show you that users crontab.  Of course, if you want to edit it, you can by doing:

    crontab -e -u username


     

  • Using SCP Aliases to Upload Files Quicker (OS X, BASH)

    15:32 on August 2, 2009 | 0 Comments Tweet This! | Digg This!
    Tags: , linux, ,

    If like me, you have a particular path on a server you always upload files to, via SCP, then you’ll probably want a better way than typing the full path into the scp command everytime you upload a file!

    This command has been tested on OS X, but there’s no reason it wouldn’t work on a Linux or BSD machine running BASH, either.

    I personally have a “stuff” directory on a web server, where I put random files to share with people, but it’s path is pretty long on the remote web server, and I have to type it everytime I run the scp command – not quick or great!

    There’s a way around it, though, by using bash aliases.  By editing the ~/.bash_profile file (.bash_profile in your home directory), we can alias common scp commands.

    So, for example, if I have a file called screenshot.png and I want it to go to /var/www/stuff on a remote server called server.example.com, I would normally have to do:

    scp screenshot.png server.example.com:/var/www/stuff

    This can get boring quick, especially if you do it a lot during the day.  We can, however, alias this to a command called whatever we want (take care though not to use an alias of an already existing command/application!)  So, if I wanted just a command of “scpstuff” I could do that by editing the ~/.bash_profile file by adding:

    alias scpstuff="scp $1 server.example.com:/var/www/stuff"

    You will need to close the terminal and reopen it for the alias to take affect, after saving the file.

    What this will do is, take the first argument to “scpstuff” (represented by $1), and run the command with it in, so, to upload something to the /var/www/stuff directory on server.example.com, all I would need to do now is:

    scpstuff screenshot.png

    You will be prompted for your SSH password as normal (unless you use SSH keys) but it’s much quicker than typing the whole line out each time!

    Of course, you could set up lots of aliases, such as scpstuff, scpimage, scpscreenshot – anything you do a lot would be useful!

     

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