Yum Broken libelf.so libs* fix centos

  • Recently while installing letsencrypt I’ve come across yum being broken {by something @ somewhere} where yum tossed an error of libelf.so.1, a python shared object.

    Where yum nor rpm was able to run.

    So I ran ldconfig, which is a program used to maintain shared libraries. This from the man pages:

    • ldconfig creates the necessary links and cache to the most recent shared libraries found in the directories specified on the command line, in the file /etc/ld.so.conf, and in the trusted directories (/lib and /usr/lib). The cache is used by the run-time linker, ld.so or ld-linux.so.

    ldconfig checks the header and filenames of the libraries it encounters when determining which versions should have their links updated.

    So I got on with it using the -v flag or verbose

    ldconfig -v


    ldconfig: /etc/ld.so.conf.d/kernel-2.6.32-573.18.1.el6.x86_64.conf:6: duplicate hwcap 1 nosegneg
    ldconfig: /etc/ld.so.conf.d/kernel-2.6.32-573.22.1.el6.x86_64.conf:6: duplicate hwcap 1 nosegneg
    ldconfig: /etc/ld.so.conf.d/kernel-2.6.32-573.26.1.el6.x86_64.conf:6: duplicate hwcap 1 nosegneg
    ldconfig: /etc/ld.so.conf.d/kernel-2.6.32-573.7.1.el6.x86_64.conf:6: duplicate hwcap 1 nosegneg
    ldconfig: /etc/ld.so.conf.d/kernel-2.6.32-573.8.1.el6.x86_64.conf:6: duplicate hwcap 1 nosegneg
    ldconfig: /etc/ld.so.conf.d/kernel-2.6.32-642.1.1.el6.x86_64.conf:6: duplicate hwcap 1 nosegneg
    	libmysqlclient.so.16 -> libmysqlclient.so.16.0.0
    	libmysqlclient_r.so.16 -> libmysqlclient_r.so.16.0.0
    	libTix.so -> libTix.so
    	libbz2.so.1 -> libbz2.so.1.0.4
    	libSegFault.so -> libSegFault.so
    	libnsl.so.1 -> libnsl-2.12.so
    	libgssapi_krb5.so.2 -> libgssapi_krb5.so.2.2
    	libgmodule-2.0.so.0 -> libgmodule-2.0.so.0.2800.8
    	libkeyutils.so.1 -> libkeyutils.so.1.3
    	libncursesw.so.5 -> libncursesw.so.5.7
    	libfreeblpriv3.so -> libfreeblpriv3.so
    	libcrypt.so.1 -> libcrypt-2.12.so
    	libanl.so.1 -> libanl-2.12.so
    	libext2fs.so.2 -> libext2fs.so.2.4
    	libutil.so.1 -> libutil-2.12.so
    	libnss_nisplus.so.2 -> libnss_nisplus-2.12.so
    	libncurses.so.5 -> libncurses.so.5.7
    	libattr.so.1 -> libattr.so.1.1.0
    	libnss_hesiod.so.2 -> libnss_hesiod-2.12.so
    	libglib-2.0.so.0 -> libglib-2.0.so.0.2800.8
    	libz.so.1 -> libz.so.1.2.3
    	libselinux.so.1 -> libselinux.so.1
    	libkrb5.so.3 -> libkrb5.so.3.3
    	libdb-4.7.so -> libdb-4.7.so
    	libc.so.6 -> libc-2.12.so
    	libthread_db.so.1 -> libthread_db-1.0.so
    	libresolv.so.2 -> libresolv-2.12.so
    	libk5crypto.so.3 -> libk5crypto.so.3.1
    	libreadline.so.6 -> libreadline.so.6.0

    And so many other shared libraries…

    ldconfig in verbose mode will spit out shared libraries and links, re caching them.

    Once this is complete I ran:

    ldd /bin/rpm

    Which from the lunux man:

    • ldd prints the shared objects (shared libraries) required by each program or shared object specified on the command line.


    linux-vdso.so.1 =>  (0x00007fffaaeba000)
    	librpmbuild.so.1 => /usr/lib64/librpmbuild.so.1 (0x00007fa244e32000)
    	librpm.so.1 => /usr/lib64/librpm.so.1 (0x00007fa244bc7000)
    	libmagic.so.1 => /usr/lib64/libmagic.so.1 (0x00007fa2449a7000)
    	librpmio.so.1 => /usr/lib64/librpmio.so.1 (0x00007fa244778000)
    	libselinux.so.1 => /lib64/libselinux.so.1 (0x00007fa244559000)
    	libcap.so.2 => /lib64/libcap.so.2 (0x00007fa244354000)
    	libacl.so.1 => /lib64/libacl.so.1 (0x00007fa24414c000)
    	libdb-4.7.so => /lib64/libdb-4.7.so (0x00007fa243dd8000)
    	libbz2.so.1 => /lib64/libbz2.so.1 (0x00007fa243bc6000)
    	liblzma.so.0 => /usr/lib64/liblzma.so.0 (0x00007fa2439a5000)
    	liblua-5.1.so => /usr/lib64/liblua-5.1.so (0x00007fa243778000)
    	libm.so.6 => /lib64/libm.so.6 (0x00007fa2434f3000)
    	libelf.so.1 => /usr/lib64/libelf.so.1 (0x00007fa2432dd000)
    	libnss3.so => /usr/lib64/libnss3.so (0x00007fa242f9d000)
    	libpopt.so.0 => /lib64/libpopt.so.0 (0x00007fa242d93000)
    	libz.so.1 => /lib64/libz.so.1 (0x00007fa242b7d000)
    	librt.so.1 => /lib64/librt.so.1 (0x00007fa242975000)
    	libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fa242757000)
    	libc.so.6 => /lib64/libc.so.6 (0x00007fa2423c3000)
    	libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fa2421ac000)
    	libdl.so.2 => /lib64/libdl.so.2 (0x00007fa241fa8000)
    	/lib64/ld-linux-x86-64.so.2 (0x00007fa24506c000)
    	libattr.so.1 => /lib64/libattr.so.1 (0x00007fa241da3000)
    	libnssutil3.so => /usr/lib64/libnssutil3.so (0x00007fa241b76000)
    	libplc4.so => /lib64/libplc4.so (0x00007fa241971000)
    	libplds4.so => /lib64/libplds4.so (0x00007fa24176d000)
    	libnspr4.so => /lib64/libnspr4.so (0x00007fa24152e000)

    Boom, problem solved. Yum is functional again.

    As note, I cannot blame this on certbot, considering this system has been beaten down as a dev / trial. break & fix whatever was the flavor of the day for the last 3++ years. So this is by far the first issue I’ve caused by intentionally wreaking havok on a system. Comes with the territory.

Tmux Commands

screen and tmux

A comparison of the features (or more-so just a table of notes for accessing some of those features) for GNU screen and BSD-licensed tmux.

The formatting here is simple enough to understand (I would hope). ^ means ctrl+, so ^x is ctrl+x. M- means meta (generally left-alt or escape)+, so M-x is left-alt+x

It should be noted that this is no where near a full feature-set of either group. This - being a cheat-sheet - is just to point out the most very basic features to get you on the road.

Trust the developers and manpage writers more than me. This document is originally from 2009 when tmux was still new - since then both of these programs have had many updates and features added (not all of which have been dutifully noted here).

Action tmux screen
start a new session tmux OR
tmux new OR
tmux new-session
re-attach a detached session tmux attach OR
tmux attach-session
re-attach an attached session (detaching it from elsewhere) tmux attach -d OR
tmux attach-session -d
screen -dr
re-attach an attached session (keeping it attached elsewhere) tmux attach OR
tmux attach-session
screen -x
detach from currently attached session ^b d OR
^b :detach
^a ^d OR
^a :detach
rename-window to newname ^b , <newname> OR
^b :rename-window <newn>
^a A <newname>
list windows ^b w ^a w
list windows in chooseable menu ^a "
go to window # ^b # ^a #
go to last-active window ^b l ^a ^a
go to next window ^b n ^a n
go to previous window ^b p ^a p
see keybindings ^b ? ^a ?
list sessions ^b s OR
tmux ls OR
tmux list-sessions
screen -ls
toggle visual bell ^a ^g
create another window ^b c ^a c
exit current shell/window ^d ^d
split window/pane horizontally ^b " ^a S
split window/pane vertically ^b % ^a |
switch to other pane ^b o ^a <tab>
kill the current pane ^b x OR (logout/^D)
collapse the current pane/split (but leave processes running) ^a X
cycle location of panes ^b ^o
swap current pane with previous ^b {
swap current pane with next ^b }
show time ^b t
show numeric values of panes ^b q
toggle zoom-state of current pane (maximize/return current pane) ^b z
break the current pane out of its window (to form new window) ^b !
re-arrange current panels within same window (different layouts) ^b [space]
Kill the current window (and all panes within) ^b killw [target-window]
  • Again running smartctl after all is said and done:

    smartctl --all /dev/sda

    ddrescue-smartctl-after-rescue.png ddrescue-smartctl-2.png

    Yet an old drive in itself, I run the wheels off of them, and monitor regularly as anyone should.

    read more
  • Clone hard drive with ddrescue

    Testing a hard drive for failure via smartmontools

    Install smartmontools if not already present: (debian)

    apt-get install smartmontools

    Locate specific hard drives currently installed:


    In this case I choose device ‘sda’

    smartctl --all /dev/sda -q errorsonly

    Example of failing hard drive: smart-failure.png

    Preparing a used hard drive for cloning

    Clearing existing partitions from destination hard drive:

    In this case the destination drive is defined as sdc:

    I’ll use fdisk to clear all existing partitions:

    fdisk /dev/sdc Then print partition existing on sdc by typing the letter p



    The above image shows some detail on the destination drive, including on FreeBSD partition named /dev/sdc4

    Since there is only one partition on the destination drive, we simply need to type the letter d at the fdisk command prompt:



    If there are more existing partitions on the destination drive, we are presented with them, and numbers to go along, we select which partition via numbers what we delete (in this case everything)


    Once we’ve removed the partitions, we type the letter w to write the changes, (actually delete the partitions)

    I type the letter p once again to make sure no partitions are still on the disk and then the letter w to write the changes:


    Using ddrescue to clone the hard drive:

    !Insure your drive letters are correct!

    The command I use to simplify the procedure including reading the damaged drive and putting as little pressure on it as we can manage, while getting as much data as we can, are as follows:

    Insure existing, or damaged hard drive first, and destination hard drive second (In other terms input file first and output file second)

    ddrescue -f -n /dev/sda /dev/sdc /root/recovery.log

    From https://linux.die.net/man/1/ddrescue

    -f, --force overwrite output device or partition

    -n, --no-split do not try to split or retry failed blocks

    We set a log file, which ddrescue can read later if for any reason the proceedure fails in the middle. Or also if we do not get as close to a 100% success rate when finished, the log file will set ddrescue to only attempt to get failed blocks on additional runs.


    In this case 100% of the data was recovered, and transferred to the new hard drive:


    I run lsblk once again to check partitions have been transferred: ddrescue-new-partitions.png

    I then restart the machine:

    shutdown -r now

    After a restart, the journal will be recovered as well as other routine scripts run. I remove other old, damaged hard drives during the restart just before the BIOS kicks up.

    Again after a restart I run :




    Note This local server is a test environment running ProxMox. Everything running as it should after the clone.

    read more