sysadmin-utils

A small collection of scripts that might be useful to sysadmins.

Contributions of new scripts are very welcome, as are suggestions for things to install.

I have a preference for Perl, but that does not rule out code that needs to be compiled, or code in other scripting languages (Python, Ruby, etc).

ago

Show how long ago a file/directory was modified in a human-readable fashion.

Example:

 $ ./ago /etc/passwd
 /etc/passwd 15 weeks ago

Alternatives:

• stat and ls both show ages, but not in a human-readable fashion.

cidr2ip

Given a set of CIDR ranges output the individual IPs in the range(s).

Example:

 $ ./cidr2ip 192.168.0.0/24
 192.168.0.0
 192.168.0.1
 192.168.0.2
 192.168.0.3
 192.168.0.4
 ..

dupes

Report on duplicate files, via a SHA1 hash of the contents, recursively.

Example:

$ dupes
./.git/logs/HEAD
./.git/logs/refs/heads/master
./.git/refs/heads/master
./.git/refs/remotes/origin/master

Alternatives:

• fdupes
• fslint
• duff
• rdfind

empty-dir

Indicate, via return code, whether a given directory is empty or not.

Example:

if empty-dir /etc; then echo "We're broken" ; fi

maybe

In a similar vain to true and false the maybe command exits with a status code of zero or one, depending on a random number.

It can be useful in scripts which need to test-failures, or which benefit from randomness:

Example:

 maybe && echo "I pass"

 maybe || echo "I fail"

multi-ping

Ping a host, regardless of whether it is an IPv6 or IPv4 host.

Example:

 $ multi-ping steve.org.uk
 Host steve.org.uk - 80.68.85.46 alive
 Host steve.org.uk - 2001:41c8:125:46:0:0:0:10 alive

Requirements:

• The Net::DNS perl module.
• The ping + ping6 binaries.

mysql-slave-check

If the current host is a MySQL slave this script will test that the slave replication is still working.

Replication is regarded as being OK if the following three conditions are true:

• The output of "SHOW SLAVE STATUS" includes: Slave_IO_Running: Yes
• The output of "SHOW SLAVE STATUS" includes: Slave_SQL_Runing: Yes
• The slave is less than 24 hours behind the master.

Example:

 # ./mysql-slave-check
 The replication appears to show an error:
 ..
 Master_Host: da-db1
 Master_User: slave
 Master_Port: 3306
 Connect_Retry: 60
 Master_Log_File: mysql-bin.000124
 Read_Master_Log_Pos: 65667
 Relay_Log_File: relay-log.001139
 Relay_Log_Pos: 27251
 Relay_Master_Log_File: mysql-bin.000124
 Slave_IO_Running: No
 Slave_SQL_Running: No
 ..

The script exits silently if all is well, unless you add "--verbose":

 # ./mysql-slave-check -v
 The slave is running, successfully.
 Replication lag: 0 seconds

Requirements:

• There must be a file /etc/mysql/debian.cnf with valid "user=" and "password=" lines.

randpass

Generate a single random password via /dev/urandom.

Example:

  $ ./randpass
  cT3j7Zp6
  $ ./randpass -n 10
  ulHrNvYLaa
  $ ./randpass -n 20 -f
  oe[d7+e.{Uw=L'RO~[]{

(Adding "-f" uses the full alphabet of possible symbols, otherwise only alpha-numeric values are shown. "-n" sets the length of the generated password.)

Existing alternatives:

• apg
• gpw
• pwgen
• ...

since

Show the new output since previously reading a file. This is useful for keeping track of logfile updates.

Example:

   $ ./since /var/log/messages >/dev/null
   $ logger "testing the log"
   $ ./since /var/log/messages
   Apr 20 11:24:37 precious skx: testing the log

splay

Sleep for a random amount of time, limited by the given max value. (Default is 5 minutes).

Example:

  $ ./splay -v
  Sleeping for 77 seconds from max splay-time of 300 seconds

  $ ./splay -v -m 20
  Sleeping for 7 seconds from max splay-time of 20 seconds

Existing alternatives:

• desync

ssl-expiry-date

Report the date, and number of days, until the given SSL certificate expires.

Example:

    ./ssl-expiry-date bbc.co.uk
    Certificate presented at : bbc.co.uk
    Expires: Jun 18 13:50:58 2013 GMT  [63 days in the future]

timeout

Timeout allows you to run a command which will be killed after the given number of seconds.

Example:

    # Kill the command after 63 seconds.
    ./timeout -t 63 top

    # Kill the command after two minutes, five seconds.
    ./timeout -t 2:5 top

    # Kill the command after three hours, five minutes, and seven seconds
    ./timeout -t 3:5:7 top

until-success

Repeat the specific command until it succeeds - run at least once always.

Example:

     ./until-success ssh example.com -l root -i ~/.ssh/example.com.key

Trivial (ba)sh alternatives:

• while true ; do $cmd; done
• watch -n 2 $cmd

when-up

Waits until a given host is online (determined by ping until executing a given command

Example:

 $ ./when-up 1.2.3.4 ssh [email protected]
 Waiting for 1.2.3.4 to come online...
 Last login: Sat Dec 28 23:25:01 2013 from 5.6.7.8
 [email protected]:~#

Alternatives:

• until-success ping -c 1 1.2.3.4; ssh [email protected]

which-shell

Identify the shell we're running under.

For example:

 $ which-shell
 dash

Existing alternatives:

• ls -l /bin/sh

with-lock

Run a command, unless an existing copy of that command is already running, via the creation of a temporary lockfile.

For example:

 with-lock rsync ...

The lockfile-name is based upon the SHA1 hash of the command to be executed and the current User-ID.

Existing alternatives:

• lckdo - Requires you to build your own lockfile name
• flock - Requires you to build your own lockfile name

Problems

Please report any issue/suggestions via the github repository:

• https://github.com/skx/sysadmin-util

Author

Steve Kemp [email protected]