disable or enable ipv6 ssh

September 20, 2016 Comments off

You may experience problems with ssh and ipv6. If so edit the /etc/ssh/sshd_config file
and enable the ListenAddress option. You can also enable (unpound) the ipv6
option ListenAddress ::.

You may experience lockouts from ssh if you have AAAA ipv6 records in your nameserver if
you don’t make theses changes.

Be sure and restart ssh after changes.

Categories: sysadmin

Check Spamassassin perl modules

June 19, 2016 Comments off

To check spamassassin and verify all required perl modules are installed
run this:

spamassassin -D –lint 2>&1 | grep -i failed

then use cpan install module::name ie
cpan install Digest::SHA1

Some additions are required to augment the default install. There is benefit
to adding missing modules as a more complete spam analysis will occur.

Categories: sysadmin

Backup/Copy mysql or mariadb database

March 19, 2016 Leave a comment

You can copy or backup all your databases with these commands including
coping to another server.

# backup
mysqldump -u root -p yourdb > mysqlbak.sql
or for dumping all databases
mysqldump –all-databases -u root -p > mysqlbakall.sql
# restore
mysql -u root -p yourdb < mysqlbak.sql
to restore all databases
mysql -u root -p < mysqlbakall.sql

Categories: sysadmin

Reset Samsung S6 (+ variants) + battery tips

February 4, 2016 Leave a comment

It is simple to reset the Samsung S6. Sometimes this is necessary to improve battery life
and performance or just remove clutter from your phone.

First us Samsung’s excellent Smart Switch software (d/l from Samsung for Windows or OSX) and
backup your phone. The software backs up all your data including sms, email settings, etc.
It is very quick also.

Then do a hard reset by holding volume up key, home key, and power key with the phone
powered off. release the home key as soon as you see the Samsung logo and you should boot
into the recovery mode.

Then select from Recovery Mode menu “wipe data / factory reset” using Volume buttons to
navigate and Power button to confirm. After restarting your phone, connect backup to
your desktop and restore your phone with Smart Switch.

You find a few apps with setup requirements but it’s mostly painless.

After months of ownership and many experiments, I have found the best setup for battery life
on my S6-active was to change wifi-settings to enable wifi only while awake (#1 battery eater if
you enable wifi while sleeping) or if you don’t need/care about data usage, leave wifi off.
Also use android email app and only sync during most important part of day (settings has ability
to sync during specified hours) for your email. You can manually sync at other times.

If you take this approach, your S6 (or at least my S6-Active) shows 50+ hours standby after a full charge.

Categories: tech-tips

Cloning mikrotik routerboard (rb7xx, rb9xx, rb11xxx)

February 1, 2016 Leave a comment

You can easily clone like routerboard hardware with these commands:

First to ssh admin@youripaddress or run terminal from winbox and run the following on the device you want to clone in this example we clone an rb751g to rb951.

## on rb751g type:
/export compact file=name

Then copy the name.rsc file to the rb951 $$either drag and drop it to files with winbox or use sftp.

hard reset the device you want to clone to by powering off and holding reset button, powering on,
and releasing reset button when led next to power plug starts to rapidly flash. Wait until the
os initializes and access with winbox.

## on rb951 type (after hard reset):
/import name.rsc ## you should see no errors.

## then on rb951 type:
/system reset run-after-reset=”name.rsc”
This will clear the current config and import the one from the rb751g

After a minute to load or so you should be able to access the rb951 with winbox and have a complete clone
of the rb751g.

Categories: sysadmin

Install libguestfs-tools and add serial console access to your vm

November 13, 2015 Leave a comment

To add serial access to your vm, with Debian/Ubuntu apt-get install libguestfs-tools.
Then with vm shutdown, execute the following:

root:~# guestmount -d vmname -i /mnt
root:~# ln -s /mnt/lib/systemd/system/getty@.service /mnt/etc/systemd/system
root:~# umount /mnt

Reboot your vm and you should have serial console access.

Categories: sysadmin

backup your kvm vm with dd

September 19, 2015 Leave a comment

The dd utility is a good way to make a backup of your kvm vm image. It
is nice to have a progress indicator so install pv (pipe viewer) to
gain this feature ..ie apt-get install pv.

Here is a backup script:

dd if=org.img | pv | dd of=backup.img bs=1M

On my system it took about 10 minutes to complete a backup of a 50g image.

Categories: sysadmin