SSH Jump and local command

I added this in my ~/.ssh/config to help avoid stupid mistakes:

Host *.prod-domain.com
    LocalCommand print "WARNING: PROD" && print "continue ?" && read
    PermitLocalCommand yes

Which makes ssh print a warning and a prompt when I try to connect to a host under prod-domain.com.

Now, most hosts do not expose ssh publically, so we have to go through a gateway. I used to do

ssh -J gateway.prod-domain.com target.prod-domain.com

But with the local command enabled, ssh fails with:

Bad packet length 1231976033.
ssh_dispatch_run_fatal: Connection to UNKNOWN port 65535: message authentication code incorrect

Connecting directly (e.g. ssh gateway.prod-domain.com) still works fine, and connecting with a jump works if I comment the local command.

Are local commands and ssh jumps incompatible ? Is it documented somewhere, and is there a way to make it work (like disabling the local command when "jumping"), or did I maybe hit a bug ?

Answer

As the ssh_config manpage says:

The command is run synchronously and does not have access to the session of the ssh(1) that spawned it. It should not be used for interactive commands.

Your problem is with the read statement, it messes up the negotiation process of SSH performed in the tunnel created via gateway.prod-domain.com.

You can configure your client so only the "endpoints" give you the warning, the gateway doesn't, by having an empty entry in your ~/.ssh/config for the gateway, like this:

Host gateway.prod-domain.com gateway
    HostName gateway.prod-domain.com

Host *.prod-domain.com
    ProxyJump gateway
    LocalCommand print "WARNING: PROD" && print "continue ?" && read
    PermitLocalCommand yes

This way, what you tried to do will work, just be sure not to use the "prod-domain" servers as a jump proxy (except for the gateway, of course). Or, to avoid interactive commands altogether, you could use something like this:

Host *.prod-domain.com
    LocalCommand echo -e "\x1b[30;41mWARNING: You are on a PRODUCTIVE system!\x1b0m"
    PermitLocalCommand yes

This way, while you can't prevent the session from establishing, you will be given a big red warning.

windows 10 - select boot device on American Megatrends BIOS Version B3W6_NA123C.029 05/05/2017 13:55:49

I am trying to boot a Laptop with the American Megatrends BIOS from a different boot device.

The setup shows Boot option priorities "Windows Boot Manager" and "UEFI: Built-in EFI...".

There is also an "OS Slelect" (!) with the options "Windows" and "Linux".

But I did not find any option to boot from USB/CD/Lan.

What do I need to do?

Answer

We can try the following ways to troubleshoot the issue:

1. We need to set the setting of "Boot From a USB Drive or CD".
   Restart your computer and wait for that first screen to pop up. Often, it’ll say something like “Press F12 to Choose Boot Device” somewhere on the screen. Press that key.

For details we can refer the article: How to Boot From a USB Drive or CD on Any Computer

2. We need to plug in the USB device or CD, if we have already plugged in the USB device or CD, it may also be that the computer does not recognize the USB or CD device, try replacing the USB device with the USB interface.




3. Turn off Secure Boot, then view if we can see the option to boot from USB/CD/Lan.

domain name system - How is DNS lookup configured for OSX Mountain Lion?

If I cat my resolv.conf, I see this message:

#
# Mac OS X Notice

#
# This file is not used by the host name and address resolution
# or the DNS query routing mechanisms used by most processes on
# this Mac OS X system.
#
# This file is automatically generated.
#

I am trying to add a DNS entry. I edited my hosts file and flushed the dns cache, but the name is not resolving if I use host servername. I thought perhaps that host was not configured to look at the hosts file. How can I get my new entry to resolve, and what is OSX using if not resolv.conf?

Answer

The host tool does not simply resolve names (as in, using the system name resolver) but actually queries dns servers (as in, sending packets to udp/53 and possibly tcp/53): it doesn't know nor use the local hosts file.

If you want to test the operating system's resolver (as in, gethostbyname() and similar libc functions) you can try to ping the name you added to /etc/hosts and it will honor what you put in that file.

Also, as you already found out DNS lookup on Mac OSX does not use /etc/resolv.conf, and the correct way to configure which DNS servers are queried is in the Network Settings gui and/or networksetup commandline tool. I honestly don't know if you can configure the order in which sources are tried, but the standard behavior is to try /etc/hosts first and dns servers after that.

postgresql - Postgres connection establishment slow

If I wan to connect to postgres 9.1.1 db on debian lenny with PgAdmin, it takes >15 seconds until the connection is established. There is nothing to see in the logs why it takes so long.

Any ideas how I can analyze the problem? Here my Configuration:

pg_hba.conf

# "local" is for Unix domain socket connections only
local   all             all                                     md5

# IPv4 local connections:
host    all             all             127.0.0.1/32            md5
host    all             all             192.168.1.0/24          md5 
# IPv6 local connections:
host    all             all             ::1/128                 md5
# Allow replication connections from localhost, by a user with the  
# replication privilege.
local   replication     postgres                                 trust
host    replication     postgres        192.168.1.0/24           trust
host    replication     postgres        ::1/128                  trust

postgresql.conf

# -----------------------------
# PostgreSQL configuration file
# -----------------------------
#
# This file consists of lines of the form:
#

#   name = value
#
# (The "=" is optional.)  Whitespace may be used.  Comments are introduced with
# "#" anywhere on a line.  The complete list of parameter names and allowed
# values can be found in the PostgreSQL documentation.
#
# The commented-out settings shown in this file represent the default values.
# Re-commenting a setting is NOT sufficient to revert it to the default value;
# you need to reload the server.
#

# This file is read on server startup and when the server receives a SIGHUP
# signal.  If you edit the file on a running system, you have to SIGHUP the
# server for the changes to take effect, or use "pg_ctl reload".  Some
# parameters, which are marked below, require a server shutdown and restart to
# take effect.
#
# Any parameter can also be given as a command-line option to the server, e.g.,
# "postgres -c log_connections=on".  Some parameters can be changed at run time
# with the "SET" SQL command.
#

# Memory units:  kB = kilobytes        Time units:  ms  = milliseconds
#                MB = megabytes                     s   = seconds
#                GB = gigabytes                     min = minutes
#                                                   h   = hours
#                                                   d   = days


#------------------------------------------------------------------------------
# FILE LOCATIONS
#------------------------------------------------------------------------------


# The default values of these variables are driven from the -D command-line
# option or PGDATA environment variable, represented here as ConfigDir.

#data_directory = 'ConfigDir'       # use data in another directory
                    # (change requires restart)
#hba_file = 'ConfigDir/pg_hba.conf' # host-based authentication file
                    # (change requires restart)
#ident_file = 'ConfigDir/pg_ident.conf' # ident configuration file
                    # (change requires restart)


# If external_pid_file is not explicitly set, no extra PID file is written.
#external_pid_file = '(none)'       # write an extra PID file
                    # (change requires restart)


#------------------------------------------------------------------------------
# CONNECTIONS AND AUTHENTICATION
#------------------------------------------------------------------------------


# - Connection Settings -

listen_addresses = '*'      # what IP address(es) to listen on;
                    # comma-separated list of addresses;
                    # defaults to 'localhost', '*' = all
                    # (change requires restart)
port = 5432             # (change requires restart)
max_connections = 300           # (change requires restart)
# Note:  Increasing max_connections costs ~400 bytes of shared memory per
# connection slot, plus lock space (see max_locks_per_transaction).

#superuser_reserved_connections = 3 # (change requires restart)
#unix_socket_directory = ''     # (change requires restart)
#unix_socket_group = ''         # (change requires restart)
#unix_socket_permissions = 0777     # begin with 0 to use octal notation
                    # (change requires restart)
#bonjour = off              # advertise server via Bonjour
                    # (change requires restart)
#bonjour_name = ''          # defaults to the computer name
                    # (change requires restart)


# - Security and Authentication -

#authentication_timeout = 1min      # 1s-600s
ssl = off               # (change requires restart)
#ssl_ciphers = 'ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH'  # allowed SSL ciphers
                    # (change requires restart)
#ssl_renegotiation_limit = 512MB    # amount of data between renegotiations
#password_encryption = on
#db_user_namespace = off


# Kerberos and GSSAPI
#krb_server_keyfile = ''
#krb_srvname = 'postgres'       # (Kerberos only)
#krb_caseins_users = off

# - TCP Keepalives -
# see "man 7 tcp" for details

#tcp_keepalives_idle = 0        # TCP_KEEPIDLE, in seconds;
                    # 0 selects the system default

#tcp_keepalives_interval = 0        # TCP_KEEPINTVL, in seconds;
                    # 0 selects the system default
#tcp_keepalives_count = 0       # TCP_KEEPCNT;
                    # 0 selects the system default


#------------------------------------------------------------------------------
# RESOURCE USAGE (except WAL)
#------------------------------------------------------------------------------


# - Memory -

shared_buffers = 512MB          # min 128kB
                    # (change requires restart)
temp_buffers = 32MB         # min 800kB
#max_prepared_transactions = 0      # zero disables the feature
                    # (change requires restart)
# Note:  Increasing max_prepared_transactions costs ~600 bytes of shared memory
# per transaction slot, plus lock space (see max_locks_per_transaction).
# It is not advisable to set max_prepared_transactions nonzero unless you

# actively intend to use prepared transactions.
#work_mem = 1MB             # min 64kB
#maintenance_work_mem = 16MB        # min 1MB
#max_stack_depth = 2MB          # min 100kB

# - Kernel Resource Usage -

#max_files_per_process = 1000       # min 25
                    # (change requires restart)
#shared_preload_libraries = ''      # (change requires restart)


# - Cost-Based Vacuum Delay -

#vacuum_cost_delay = 0ms        # 0-100 milliseconds
#vacuum_cost_page_hit = 1       # 0-10000 credits
#vacuum_cost_page_miss = 10     # 0-10000 credits
#vacuum_cost_page_dirty = 20        # 0-10000 credits
#vacuum_cost_limit = 200        # 1-10000 credits

# - Background Writer -


#bgwriter_delay = 200ms         # 10-10000ms between rounds
#bgwriter_lru_maxpages = 100        # 0-1000 max buffers written/round
#bgwriter_lru_multiplier = 2.0      # 0-10.0 multipler on buffers scanned/round

# - Asynchronous Behavior -

#effective_io_concurrency = 1       # 1-1000. 0 disables prefetching



#------------------------------------------------------------------------------
# WRITE AHEAD LOG
#------------------------------------------------------------------------------

# - Settings -

wal_level = hot_standby         # minimal, archive, or hot_standby
                    # (change requires restart)
fsync = on              # turns forced synchronization on or off
synchronous_commit = on     # synchronization level; on, off, or local

wal_sync_method = fsync     # the default is the first option
                    # supported by the operating system:
                    #   open_datasync
                    #   fdatasync (default on Linux)
                    #   fsync
                    #   fsync_writethrough
                    #   open_sync
#full_page_writes = on          # recover from partial page writes
#wal_buffers = -1           # min 32kB, -1 sets based on shared_buffers
                    # (change requires restart)

#wal_writer_delay = 200ms       # 1-10000 milliseconds

#commit_delay = 0           # range 0-100000, in microseconds
#commit_siblings = 5            # range 1-1000

# - Checkpoints -

#checkpoint_segments = 3        # in logfile segments, min 1, 16MB each
#checkpoint_timeout = 5min      # range 30s-1h
#checkpoint_completion_target = 0.5 # checkpoint target duration, 0.0 - 1.0

#checkpoint_warning = 30s       # 0 disables

# - Archiving -

archive_mode = on                                   # allows archiving to be done
                                            # (change requires restart)
archive_command = 'cp -i %p /opt/postgres/9.1/archive/%f'   # command to use to archive a logfile segment
#archive_timeout = 0        # force a logfile segment switch after this
                # number of seconds; 0 disables



#------------------------------------------------------------------------------
# REPLICATION
#------------------------------------------------------------------------------

# - Master Server -

# These settings are ignored on a standby server

max_wal_senders = 10        # max number of walsender processes

                # (change requires restart)
#wal_sender_delay = 1s      # walsender cycle time, 1-10000 milliseconds
#wal_keep_segments = 0      # in logfile segments, 16MB each; 0 disables
#vacuum_defer_cleanup_age = 0   # number of xacts by which cleanup is delayed
#replication_timeout = 60s  # in milliseconds; 0 disables
#synchronous_standby_names = '' # standby servers that provide sync rep
                # comma-separated list of application_name
                # from standby(s); '*' = all

# - Standby Servers -


# These settings are ignored on a master server

#hot_standby = off          # "on" allows queries during recovery
                    # (change requires restart)
#max_standby_archive_delay = 30s    # max delay before canceling queries
                    # when reading WAL from archive;
                    # -1 allows indefinite delay
#max_standby_streaming_delay = 30s  # max delay before canceling queries
                    # when reading streaming WAL;

                    # -1 allows indefinite delay
#wal_receiver_status_interval = 10s # send replies at least this often
                    # 0 disables
#hot_standby_feedback = off     # send info from standby to prevent
                    # query conflicts


#------------------------------------------------------------------------------
# QUERY TUNING
#------------------------------------------------------------------------------


# - Planner Method Configuration -

#enable_bitmapscan = on
#enable_hashagg = on
#enable_hashjoin = on
#enable_indexscan = on
#enable_material = on
#enable_mergejoin = on
#enable_nestloop = on

#enable_seqscan = on
#enable_sort = on
#enable_tidscan = on

# - Planner Cost Constants -

#seq_page_cost = 1.0            # measured on an arbitrary scale
#random_page_cost = 4.0         # same scale as above
#cpu_tuple_cost = 0.01          # same scale as above
#cpu_index_tuple_cost = 0.005       # same scale as above

#cpu_operator_cost = 0.0025     # same scale as above
#effective_cache_size = 128MB

# - Genetic Query Optimizer -

#geqo = on
#geqo_threshold = 12
#geqo_effort = 5            # range 1-10
#geqo_pool_size = 0         # selects default based on effort
#geqo_generations = 0           # selects default based on effort

#geqo_selection_bias = 2.0      # range 1.5-2.0
#geqo_seed = 0.0            # range 0.0-1.0

# - Other Planner Options -

#default_statistics_target = 100    # range 1-10000
#constraint_exclusion = partition   # on, off, or partition
#cursor_tuple_fraction = 0.1        # range 0.0-1.0
#from_collapse_limit = 8
#join_collapse_limit = 8        # 1 disables collapsing of explicit

                    # JOIN clauses


#------------------------------------------------------------------------------
# ERROR REPORTING AND LOGGING
#------------------------------------------------------------------------------

# - Where to Log -

#log_destination = 'stderr'     # Valid values are combinations of

                    # stderr, csvlog, syslog, and eventlog,
                    # depending on platform.  csvlog
                    # requires logging_collector to be on.

# This is used when logging to stderr:
#logging_collector = off        # Enable capturing of stderr and csvlog
                    # into log files. Required to be on for
                    # csvlogs.
                    # (change requires restart)


# These are only used if logging_collector is on:
log_directory = 'pg_log'        # directory where log files are written,
                    # can be absolute or relative to PGDATA
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log' # log file name pattern,
                    # can include strftime() escapes
#log_file_mode = 0600           # creation mode for log files,
                    # begin with 0 to use octal notation
#log_truncate_on_rotation = off     # If on, an existing log file with the
                    # same name as the new log file will be
                    # truncated rather than appended to.

                    # But such truncation only occurs on
                    # time-driven rotation, not on restarts
                    # or size-driven rotation.  Default is
                    # off, meaning append to existing files
                    # in all cases.
#log_rotation_age = 1d          # Automatic rotation of logfiles will
                    # happen after that time.  0 disables.
log_rotation_size = 10MB        # Automatic rotation of logfiles will
                    # happen after that much log output.
                    # 0 disables.


# These are relevant when logging to syslog:
#syslog_facility = 'LOCAL0'
#syslog_ident = 'postgres'

#silent_mode = off          # Run server silently.
                    # DO NOT USE without syslog or
                    # logging_collector
                    # (change requires restart)



# - When to Log -

#client_min_messages = notice       # values in order of decreasing detail:
                    #   debug5
                    #   debug4
                    #   debug3
                    #   debug2
                    #   debug1
                    #   log

                    #   notice
                    #   warning
                    #   error

log_min_messages = warning      # values in order of decreasing detail:
                    #   debug5
                    #   debug4
                    #   debug3
                    #   debug2
                    #   debug1

                    #   info
                    #   notice
                    #   warning
                    #   error
                    #   log
                    #   fatal
                    #   panic

log_min_error_statement = error # values in order of decreasing detail:
                    #   debug5

                    #   debug4
                    #   debug3
                    #   debug2
                    #   debug1
                    #   info
                    #   notice
                    #   warning
                    #   error
                    #   log
                    #   fatal

                    #   panic (effectively off)

#log_min_duration_statement = -1    # -1 is disabled, 0 logs all statements
                    # and their durations, > 0 logs only
                    # statements running at least this number
                    # of milliseconds


# - What to Log -


#debug_print_parse = off
#debug_print_rewritten = off
#debug_print_plan = off
#debug_pretty_print = on
#log_checkpoints = off
log_connections = on
#log_disconnections = off
#log_duration = off
log_error_verbosity = verbose       # terse, default, or verbose messages
log_hostname = on

#log_line_prefix = ''           # special values:
                    #   %a = application name
                    #   %u = user name
                    #   %d = database name
                    #   %r = remote host and port
                    #   %h = remote host
                    #   %p = process ID
                    #   %t = timestamp without milliseconds
                    #   %m = timestamp with milliseconds
                    #   %i = command tag

                    #   %e = SQL state
                    #   %c = session ID
                    #   %l = session line number
                    #   %s = session start timestamp
                    #   %v = virtual transaction ID
                    #   %x = transaction ID (0 if none)
                    #   %q = stop here in non-session
                    #        processes
                    #   %% = '%'
                    # e.g. '<%u%%%d> '

log_lock_waits = on         # log lock waits >= deadlock_timeout
#log_statement = 'none'         # none, ddl, mod, all
#log_temp_files = -1            # log temporary files equal or larger
                    # than the specified size in kilobytes;
                    # -1 disables, 0 logs all temp files
#log_timezone = '(defaults to server environment setting)'


#------------------------------------------------------------------------------
# RUNTIME STATISTICS

#------------------------------------------------------------------------------

# - Query/Index Statistics Collector -

#track_activities = on
#track_counts = on
#track_functions = none         # none, pl, all
#track_activity_query_size = 1024   # (change requires restart)
#update_process_title = on
#stats_temp_directory = 'pg_stat_tmp'



# - Statistics Monitoring -

#log_parser_stats = off
#log_planner_stats = off
#log_executor_stats = off
#log_statement_stats = off



#------------------------------------------------------------------------------
# AUTOVACUUM PARAMETERS
#------------------------------------------------------------------------------

autovacuum = on         # Enable autovacuum subprocess?  'on'
                    # requires track_counts to also be on.
log_autovacuum_min_duration = 10000 # -1 disables, 0 logs all actions and
                    # their durations, > 0 logs only
                    # actions running at least this number
                    # of milliseconds.

autovacuum_max_workers = 5      # max number of autovacuum subprocesses
                    # (change requires restart)
autovacuum_naptime = 5min       # time between autovacuum runs
autovacuum_vacuum_threshold = 50    # min number of row updates before
                    # vacuum
autovacuum_analyze_threshold = 50   # min number of row updates before
                    # analyze
autovacuum_vacuum_scale_factor = 0.2    # fraction of table size before vacuum
autovacuum_analyze_scale_factor = 0.1   # fraction of table size before analyze
autovacuum_freeze_max_age = 200000000   # maximum XID age before forced vacuum

                    # (change requires restart)
autovacuum_vacuum_cost_delay = 20ms # default vacuum cost delay for
                    # autovacuum, in milliseconds;
                    # -1 means use vacuum_cost_delay
autovacuum_vacuum_cost_limit = -1   # default vacuum cost limit for
                    # autovacuum, -1 means use
                    # vacuum_cost_limit


#------------------------------------------------------------------------------

# CLIENT CONNECTION DEFAULTS
#------------------------------------------------------------------------------

# - Statement Behavior -

#search_path = '"$user",public'     # schema names
#default_tablespace = ''        # a tablespace name, '' uses the default
#temp_tablespaces = ''          # a list of tablespace names, '' uses
                    # only default tablespace
#check_function_bodies = on

#default_transaction_isolation = 'read committed'
#default_transaction_read_only = off
#default_transaction_deferrable = off
#session_replication_role = 'origin'
#statement_timeout = 0          # in milliseconds, 0 is disabled
#vacuum_freeze_min_age = 50000000
#vacuum_freeze_table_age = 150000000
#bytea_output = 'hex'           # hex, escape
#xmlbinary = 'base64'
#xmloption = 'content'


# - Locale and Formatting -

datestyle = 'iso, dmy'
#intervalstyle = 'postgres'
#timezone = '(defaults to server environment setting)'
#timezone_abbreviations = 'Default'     # Select the set of available time zone
                    # abbreviations.  Currently, there are
                    #   Default
                    #   Australia

                    #   India
                    # You can create your own file in
                    # share/timezonesets/.
#extra_float_digits = 0         # min -15, max 3
#client_encoding = sql_ascii        # actually, defaults to database
                    # encoding

# These settings are initialized by initdb, but they can be changed.
lc_messages = 'de_DE.UTF-8'         # locale for system error message
                    # strings

lc_monetary = 'de_DE.UTF-8'         # locale for monetary formatting
lc_numeric = 'de_DE.UTF-8'          # locale for number formatting
lc_time = 'de_DE.UTF-8'             # locale for time formatting

# default configuration for text search
default_text_search_config = 'pg_catalog.german'

# - Other Defaults -

#dynamic_library_path = '$libdir'

#local_preload_libraries = ''


#------------------------------------------------------------------------------
# LOCK MANAGEMENT
#------------------------------------------------------------------------------

#deadlock_timeout = 1s
#max_locks_per_transaction = 64     # min 10
                    # (change requires restart)

# Note:  Each lock table slot uses ~270 bytes of shared memory, and there are
# max_locks_per_transaction * (max_connections + max_prepared_transactions)
# lock table slots.
#max_pred_locks_per_transaction = 64    # min 10
                    # (change requires restart)

#------------------------------------------------------------------------------
# VERSION/PLATFORM COMPATIBILITY
#------------------------------------------------------------------------------


# - Previous PostgreSQL Versions -

#array_nulls = on
#backslash_quote = safe_encoding    # on, off, or safe_encoding
#default_with_oids = off
#escape_string_warning = on
#lo_compat_privileges = off
#quote_all_identifiers = off
#sql_inheritance = on
#standard_conforming_strings = on

#synchronize_seqscans = on

# - Other Platforms and Clients -

#transform_null_equals = off


#------------------------------------------------------------------------------
# ERROR HANDLING
#------------------------------------------------------------------------------


#exit_on_error = off                # terminate session on any error?
#restart_after_crash = on           # reinitialize after backend crash?


#------------------------------------------------------------------------------
# CUSTOMIZED OPTIONS
#------------------------------------------------------------------------------

#custom_variable_classes = ''       # list of custom variable class names

Answer

My best guess: You're using host name lookups in pg_hba.conf - and it makes PostgreSQL perform DNS queries that fail. You're still able to connect, because it hits a rule further down the road.

You can also try turning off log_hostname on postgresql.conf.

To rule out lookups entirely, you could add the client in the hosts-file of the server.

linux - find: equal file size limit but different unit returns different result

I noticed that the these two commands to list files below 5 GiB produce different results:

find . -type f -size -5368709120c
find . -type f -size -5G

Specifically the one that uses kilobyte unit (5368709120c) returns additional files that are larger than the maximum file size returned by the one that uses the GiB unit (5G).

From the find manual page I read the following:

-size n[cwbkMG]
          File uses n units of space.  The following suffixes can be used:
          `b'    for 512-byte blocks (this is the default if no suffix is used)
          `c'    for bytes
          `w'    for two-byte words
          `k'    for Kilobytes (units of 1024 bytes)
          `M'    for Megabytes (units of 1048576 bytes)
          `G'    for Gigabytes (units of 1073741824 bytes)


The size does not count indirect blocks, but it does count blocks 
in sparse files that are not actually allocated.  Bear in mind that the `%k'
and `%b' format specifiers of -printf handle sparse files differently.   The 
`b'  suffix always denotes 512-byte blocks and never 1 Kilobyte blocks, 
which is different to the behaviour of -ls.

So, given that the unit of G is 1073741824, 5G should be 5368709120c. Is the issue due to how sparse or indirect blocks are counted?

Thanks in advance for the help.

** UPDATE **

Found something else odd. The threshold at which the files returned are different is exactly 4 GiB:

Largest file found by -5G:

4285018593 bytes = 3.990734548 GiB

Largest not file found by -5G:

4299230968 bytes = 4.003970854 GiB

Files are stored on a XFS partition:

meta-data=/dev/mapper/vg_XXXXX_lv isize=256    agcount=197, agsize=268435440 blks
         =                       sectsz=4096  attr=2, projid32bit=1
         =                       crc=0        finobt=0

data     =                       bsize=4096   blocks=52739701760, imaxpct=1
         =                       sunit=16     swidth=256 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
log      =internal               bsize=4096   blocks=521728, version=2
         =                       sectsz=4096  sunit=1 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

memory - Upgrading ram in a PC

I need to upgrade my ram in my windows pc. Ram has always confused me with the different kinds that are out there now.

I currently only have 1gb and would like to upgrade to 4gb if possible. I pulled out one of the 512mb sticks to look at it, it says it is PC2-4200. DOes this mean to upgrade I just need to make sure the new ram is PC-2 4200? Or could something else go in?

I have an older stick of ram I tried to put in earliar, its dimensions are the exact same as the stick I took out except the groove/line near the center of the ram was off by a few centimeters so it would not fit, the writing on this ram is KVR333/512 2.5v Kingston

Answer

Crucial.com has a "Scan my system" button right on their front page that will figure everything out for you.

Batch removal of special characters from file names in Linux

I am seeking to remove all special characters from several files' worth of downloaded .pdfs, and came across exactly the solution I was looking for, albeit in an OS X environment:

function to automatically remove special characters from file names during saving in MacOS X.

Could a similar method--either using sed or some other function--be implemented in a Linux environment?

Answer

You can do this with the rename command. If you are in the folder with the .pdf files with special characters:

rename 's/[^a-zA-Z0-9]//g' *.pdf

This will remove any characters from files ending in .pdf that are not A-Z in either case, or numbers. You can add to this list:

rename 's/[^a-zA-Z0-9_]//g' *.pdf

This version allows underscores.